FTBFS qt 6.2.0 on clang 11 libc++

[660/1315] Building CXX object qtbase/src/gui/CMakeFiles/Gui.dir/kernel/qhighdpiscaling.cpp.o
FAILED: qtbase/src/gui/CMakeFiles/Gui.dir/kernel/qhighdpiscaling.cpp.o 
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-DHAS_STICKY_DIR_BIT -DU_STATIC_IMPLEMENTATION -DPKGCONFIG_IS_STATIC -Wall -Wextra -fno-exceptions -fPIC -std=c++17 -Winvalid-pch -Xclang -include-pch -Xclang /home/conan/w/BuildSingleReference/.conan/data/qt/6.2.0/_/_/build/c8d84de17981661e5368b2aa872e1ac87b4fb3c3/qtbase/src/gui/CMakeFiles/Gui.dir/cmake_pch.hxx.pch -Xclang -include -Xclang /home/conan/w/BuildSingleReference/.conan/data/qt/6.2.0/_/_/build/c8d84de17981661e5368b2aa872e1ac87b4fb3c3/qtbase/src/gui/CMakeFiles/Gui.dir/cmake_pch.hxx -MD -MT qtbase/src/gui/CMakeFiles/Gui.dir/kernel/qhighdpiscaling.cpp.o -MF qtbase/src/gui/CMakeFiles/Gui.dir/kernel/qhighdpiscaling.cpp.o.d -o qtbase/src/gui/CMakeFiles/Gui.dir/kernel/qhighdpiscaling.cpp.o -c /home/conan/w/BuildSingleReference/.conan/data/qt/6.2.0/_/_/source/qt6/qtbase/src/gui/kernel/qhighdpiscaling.cpp
/home/conan/w/BuildSingleReference/.conan/data/qt/6.2.0/_/_/source/qt6/qtbase/src/gui/kernel/qhighdpiscaling.cpp:72:12: error: no viable constructor or deduction guide for deduction of template arguments of 'optional'
    return std::optional(qEnvironmentVariable(name));
           ^
/usr/include/c++/v1/optional:683:41: note: candidate template ignored: couldn't infer template argument '_Tp'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(nullopt_t) noexcept {}
                                        ^
/usr/include/c++/v1/optional:689:24: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr explicit optional(in_place_t, _Args&&... __args)
                       ^
/usr/include/c++/v1/optional:703:15: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr optional(_Up&& __v)
              ^
/usr/include/c++/v1/optional:710:24: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr explicit optional(_Up&& __v)
                       ^
/usr/include/c++/v1/optional:579:7: note: candidate template ignored: could not match 'optional<_Tp>' against 'QString'
class optional
      ^
/usr/include/c++/v1/optional:681:41: note: candidate template ignored: could not match 'optional<_Tp>' against 'QString'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(const optional&) = default;
                                        ^
/usr/include/c++/v1/optional:682:41: note: candidate template ignored: could not match 'optional<_Tp>' against 'QString'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(optional&&) = default;
                                        ^
/usr/include/c++/v1/optional:718:5: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'QString'
    optional(const optional<_Up>& __v)
    ^
/usr/include/c++/v1/optional:726:14: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'QString'
    explicit optional(const optional<_Up>& __v)
             ^
/usr/include/c++/v1/optional:736:5: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'QString'
    optional(optional<_Up>&& __v)
    ^
/usr/include/c++/v1/optional:744:14: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'QString'
    explicit optional(optional<_Up>&& __v)
             ^
/usr/include/c++/v1/optional:680:41: note: candidate function template not viable: requires 0 arguments, but 1 was provided
    _LIBCPP_INLINE_VISIBILITY constexpr optional() noexcept {}
                                        ^
/usr/include/c++/v1/optional:696:24: note: candidate function template not viable: requires at least 2 arguments, but 1 was provided
    constexpr explicit optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
                       ^
/home/conan/w/BuildSingleReference/.conan/data/qt/6.2.0/_/_/source/qt6/qtbase/src/gui/kernel/qhighdpiscaling.cpp:80:12: error: no viable constructor or deduction guide for deduction of template arguments of 'optional'
    return std::optional(qgetenv(name));
           ^
/usr/include/c++/v1/optional:683:41: note: candidate template ignored: couldn't infer template argument '_Tp'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(nullopt_t) noexcept {}
                                        ^
/usr/include/c++/v1/optional:689:24: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr explicit optional(in_place_t, _Args&&... __args)
                       ^
/usr/include/c++/v1/optional:703:15: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr optional(_Up&& __v)
              ^
/usr/include/c++/v1/optional:710:24: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr explicit optional(_Up&& __v)
                       ^
/usr/include/c++/v1/optional:579:7: note: candidate template ignored: could not match 'optional<_Tp>' against 'QByteArray'
class optional
      ^
/usr/include/c++/v1/optional:681:41: note: candidate template ignored: could not match 'optional<_Tp>' against 'QByteArray'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(const optional&) = default;
                                        ^
/usr/include/c++/v1/optional:682:41: note: candidate template ignored: could not match 'optional<_Tp>' against 'QByteArray'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(optional&&) = default;
                                        ^
/usr/include/c++/v1/optional:718:5: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'QByteArray'
    optional(const optional<_Up>& __v)
    ^
/usr/include/c++/v1/optional:726:14: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'QByteArray'
    explicit optional(const optional<_Up>& __v)
             ^
/usr/include/c++/v1/optional:736:5: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'QByteArray'
    optional(optional<_Up>&& __v)
    ^
/usr/include/c++/v1/optional:744:14: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'QByteArray'
    explicit optional(optional<_Up>&& __v)
             ^
/usr/include/c++/v1/optional:680:41: note: candidate function template not viable: requires 0 arguments, but 1 was provided
    _LIBCPP_INLINE_VISIBILITY constexpr optional() noexcept {}
                                        ^
/usr/include/c++/v1/optional:696:24: note: candidate function template not viable: requires at least 2 arguments, but 1 was provided
    constexpr explicit optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
                       ^
/home/conan/w/BuildSingleReference/.conan/data/qt/6.2.0/_/_/source/qt6/qtbase/src/gui/kernel/qhighdpiscaling.cpp:87:21: error: no viable constructor or deduction guide for deduction of template arguments of 'optional'
    auto opt = ok ? std::optional(value) : std::nullopt;
                    ^
/usr/include/c++/v1/optional:683:41: note: candidate template ignored: couldn't infer template argument '_Tp'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(nullopt_t) noexcept {}
                                        ^
/usr/include/c++/v1/optional:689:24: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr explicit optional(in_place_t, _Args&&... __args)
                       ^
/usr/include/c++/v1/optional:703:15: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr optional(_Up&& __v)
              ^
/usr/include/c++/v1/optional:710:24: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr explicit optional(_Up&& __v)
                       ^
/usr/include/c++/v1/optional:579:7: note: candidate template ignored: could not match 'optional<_Tp>' against 'int'
class optional
      ^
/usr/include/c++/v1/optional:681:41: note: candidate template ignored: could not match 'optional<_Tp>' against 'const int'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(const optional&) = default;
                                        ^
/usr/include/c++/v1/optional:682:41: note: candidate template ignored: could not match 'optional<_Tp>' against 'const int'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(optional&&) = default;
                                        ^
/usr/include/c++/v1/optional:718:5: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'const int'
    optional(const optional<_Up>& __v)
    ^
/usr/include/c++/v1/optional:726:14: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'const int'
    explicit optional(const optional<_Up>& __v)
             ^
/usr/include/c++/v1/optional:736:5: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'const int'
    optional(optional<_Up>&& __v)
    ^
/usr/include/c++/v1/optional:744:14: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'const int'
    explicit optional(optional<_Up>&& __v)
             ^
/usr/include/c++/v1/optional:680:41: note: candidate function template not viable: requires 0 arguments, but 1 was provided
    _LIBCPP_INLINE_VISIBILITY constexpr optional() noexcept {}
                                        ^
/usr/include/c++/v1/optional:696:24: note: candidate function template not viable: requires at least 2 arguments, but 1 was provided
    constexpr explicit optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
                       ^
/home/conan/w/BuildSingleReference/.conan/data/qt/6.2.0/_/_/source/qt6/qtbase/src/gui/kernel/qhighdpiscaling.cpp:98:17: error: no viable constructor or deduction guide for deduction of template arguments of 'optional'
    return ok ? std::optional(value) : std::nullopt;
                ^
/usr/include/c++/v1/optional:683:41: note: candidate template ignored: couldn't infer template argument '_Tp'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(nullopt_t) noexcept {}
                                        ^
/usr/include/c++/v1/optional:689:24: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr explicit optional(in_place_t, _Args&&... __args)
                       ^
/usr/include/c++/v1/optional:703:15: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr optional(_Up&& __v)
              ^
/usr/include/c++/v1/optional:710:24: note: candidate template ignored: couldn't infer template argument '_Tp'
    constexpr explicit optional(_Up&& __v)
                       ^
/usr/include/c++/v1/optional:579:7: note: candidate template ignored: could not match 'optional<_Tp>' against 'double'
class optional
      ^
/usr/include/c++/v1/optional:681:41: note: candidate template ignored: could not match 'optional<_Tp>' against 'const double'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(const optional&) = default;
                                        ^
/usr/include/c++/v1/optional:682:41: note: candidate template ignored: could not match 'optional<_Tp>' against 'const double'
    _LIBCPP_INLINE_VISIBILITY constexpr optional(optional&&) = default;
                                        ^
/usr/include/c++/v1/optional:718:5: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'const double'
    optional(const optional<_Up>& __v)
    ^
/usr/include/c++/v1/optional:726:14: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'const double'
    explicit optional(const optional<_Up>& __v)
             ^
/usr/include/c++/v1/optional:736:5: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'const double'
    optional(optional<_Up>&& __v)
    ^
/usr/include/c++/v1/optional:744:14: note: candidate template ignored: could not match 'optional<type-parameter-0-1>' against 'const double'
    explicit optional(optional<_Up>&& __v)
             ^
/usr/include/c++/v1/optional:680:41: note: candidate function template not viable: requires 0 arguments, but 1 was provided
    _LIBCPP_INLINE_VISIBILITY constexpr optional() noexcept {}
                                        ^
/usr/include/c++/v1/optional:696:24: note: candidate function template not viable: requires at least 2 arguments, but 1 was provided
    constexpr explicit optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
                       ^
4 errors generated.