QWaylandShmBuffer needs to handle return value from QFile::open()

FAILED: qtwayland/src/client/CMakeFiles/WaylandClient.dir/qwaylandshmbackingstore.cpp.o 
/usr/lib/ccache/bin/c++ -DQT_ASCII_CAST_WARNINGS -DQT_BUILDING_QT -DQT_BUILD_WAYLANDCLIENT_LIB -DQT_CORE_LIB -DQT_DEPRECATED_WARNINGS -DQT_EXPLICIT_QFILE_CONSTRUCTION_FROM_PATH -DQT_GUI_LIB -DQT_MOC_COMPAT -DQT_NO_AS_CONST=1 -DQT_NO_CAST_TO_ASCII -DQT_NO_CONTEXTLESS_CONNECT=1 -DQT_NO_EXCEPTIONS -DQT_NO_FOREACH -DQT_NO_FOREACH=1 -DQT_NO_JAVA_STYLE_ITERATORS -DQT_NO_NARROWING_CONVERSIONS_IN_CONNECT -DQT_NO_QASCONST -DQT_NO_QEXCHANGE -DQT_NO_QSNPRINTF -DQT_NO_STD_FORMAT_SUPPORT -DQT_STRICT_QLIST_ITERATORS -DQT_USE_QSTRINGBUILDER -DQT_WAYLANDGLOBAL_LIB -DWaylandClient_EXPORTS -D_GLIBCXX_ASSERTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -I/home/rutledge/dev/qt6-dbg/qtwayland/src/client/WaylandClient_autogen/include -I/home/rutledge/dev/qt6-dbg/qtbase/include -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtWaylandClient -I/home/rutledge/dev/qt6/qtwayland/src/client -I/home/rutledge/dev/qt6-dbg/qtwayland/src/client -I/home/rutledge/dev/qt6/qtwayland/src/client/../shared -I/home/rutledge/dev/qt6/qtwayland/src/client/global -I/home/rutledge/dev/qt6/qtwayland/src/client/hardwareintegration -I/home/rutledge/dev/qt6/qtwayland/src/client/inputdeviceintegration -I/home/rutledge/dev/qt6/qtwayland/src/client/shellintegration -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtWaylandClient/6.9.0 -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtWaylandClient/6.9.0/QtWaylandClient -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtCore -I/home/rutledge/dev/qt6-dbg/qtbase/mkspecs/linux-g++ -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtGui -I/home/rutledge/dev/qt6-dbg/qtbase/src/corelib -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtCore/6.10.0 -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtCore/6.10.0/QtCore -I/home/rutledge/dev/qt6-dbg/qtbase/src/gui -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtGui/6.10.0 -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtGui/6.10.0/QtGui -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtWaylandGlobal -I/home/rutledge/dev/qt6/qtwayland/src -I/home/rutledge/dev/qt6-dbg/qtwayland/src -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtWaylandGlobal/6.9.0 -I/home/rutledge/dev/qt6-dbg/qtbase/include/QtWaylandGlobal/6.9.0/QtWaylandGlobal -g -std=gnu++17 -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -fdiagnostics-color=always -Wall -Wextra -fPIC -Werror -Wno-error=cpp -Wno-error=deprecated-declarations -Wno-error=strict-overflow -Wno-error=implicit-fallthrough -Wno-error=deprecated-copy -Wno-error=redundant-move -Wno-error=init-list-lifetime -Wno-error=format-overflow -Wno-error=stringop-overflow -Wno-error=stringop-overread -Wno-error=deprecated-enum-enum-conversion -Wno-error=deprecated-enum-float-conversion -Wsuggest-override -fcf-protection=full -ftrivial-auto-var-init=pattern -fstack-protector-strong -fstack-clash-protection -fno-exceptions -MD -MT qtwayland/src/client/CMakeFiles/WaylandClient.dir/qwaylandshmbackingstore.cpp.o -MF qtwayland/src/client/CMakeFiles/WaylandClient.dir/qwaylandshmbackingstore.cpp.o.d -o qtwayland/src/client/CMakeFiles/WaylandClient.dir/qwaylandshmbackingstore.cpp.o -c /home/rutledge/dev/qt6/qtwayland/src/client/qwaylandshmbackingstore.cpp
/home/rutledge/dev/qt6/qtwayland/src/client/qwaylandshmbackingstore.cpp: In constructor ‘QtWaylandClient::QWaylandShmBuffer::QWaylandShmBuffer(QtWaylandClient::QWaylandDisplay*, const QSize&, QImage::Format, qreal)’:
/home/rutledge/dev/qt6/qtwayland/src/client/qwaylandshmbackingstore.cpp:67:22: error: ignoring return value of ‘bool QTemporaryFile::open()’, declared with attribute ‘nodiscard’ [-Werror=unused-result]
   67 |         tmpFile->open();
      |         ~~~~~~~~~~~~~^~
In file included from /home/rutledge/dev/qt6-dbg/qtbase/include/QtCore/qtemporaryfile.h:1,
                 from /home/rutledge/dev/qt6/qtwayland/src/client/qwaylandshmbackingstore.cpp:12:
/home/rutledge/dev/qt6/qtbase/src/corelib/io/qtemporaryfile.h:51:32: note: declared here
   51 |     QFILE_MAYBE_NODISCARD bool open() { return open(QIODevice::ReadWrite); }
      |                                ^~~~
/home/rutledge/dev/qt6/qtwayland/src/client/qwaylandshmbackingstore.cpp:71:19: error: ignoring return value of ‘bool QFile::open(int, QIODeviceBase::OpenMode, QFileDevice::FileHandleFlags)’, declared with attribute ‘nodiscard’ [-Werror=unused-result]
   71 |         file->open(fd, QIODevice::ReadWrite | QIODevice::Unbuffered, QFile::AutoCloseHandle);
      |         ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /home/rutledge/dev/qt6-dbg/qtbase/include/QtCore/qfile.h:1,
                 from /home/rutledge/dev/qt6/qtbase/src/corelib/io/qtemporaryfile.h:8:
/home/rutledge/dev/qt6/qtbase/src/corelib/io/qfile.h:289:32: note: declared here
  289 |     QFILE_MAYBE_NODISCARD bool open(int fd, OpenMode ioFlags, FileHandleFlags handleFlags=DontCloseHandle);
      |                                ^~~~
cc1plus: all warnings being treated as errors