QtLocation build failure - enum value out of range

During a full rebuild of sources, QtLocation build would consistently fail with error message stating that an enum value was out of range. Error has not been encountered with this package previously. Suspect regression.

Error Output:

In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/src/mbgl/annotation/annotation_manager.cpp:1:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/src/mbgl/annotation/annotation_manager.hpp:4:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/src/mbgl/annotation/symbol_annotation_impl.hpp:24:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/geometry.hpp:17:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/geometry/geometry.hpp:43:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/geometry/core/radian_access.hpp:26:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/numeric/conversion/cast.hpp:33:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/numeric/conversion/converter.hpp:13:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/numeric/conversion/conversion_traits.hpp:13:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/numeric/conversion/detail/conversion_traits.hpp:18:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/numeric/conversion/detail/int_float_mixture.hpp:19:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/mpl/integral_c.hpp:32:
/var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/mpl/aux_/integral_wrapper.hpp:73:31: error: 
      integer value -1 is outside the valid range of values [0, 3] for this enumeration type [-Wenum-constexpr-conversion]
    typedef AUX_WRAPPER_INST( BOOST_MPL_AUX_STATIC_CAST(AUX_WRAPPER_VALUE_TYPE, (value - 1)) ) prior;
                              ^
/var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/mpl/aux_/static_cast.hpp:24:47: note: 
      expanded from macro 'BOOST_MPL_AUX_STATIC_CAST'
#   define BOOST_MPL_AUX_STATIC_CAST(T, expr) static_cast<T>(expr)
                                              ^
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/src/mbgl/annotation/annotation_manager.cpp:1:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/src/mbgl/annotation/annotation_manager.hpp:4:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/src/mbgl/annotation/symbol_annotation_impl.hpp:24:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/geometry.hpp:17:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/geometry/geometry.hpp:43:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/geometry/core/radian_access.hpp:26:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/numeric/conversion/cast.hpp:33:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/numeric/conversion/converter.hpp:13:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/numeric/conversion/conversion_traits.hpp:13:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/numeric/conversion/detail/conversion_traits.hpp:18:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/numeric/conversion/detail/int_float_mixture.hpp:19:
In file included from /var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/mpl/integral_c.hpp:32:
/var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/mpl/aux_/integral_wrapper.hpp:73:31: error: 
      integer value -1 is outside the valid range of values [0, 3] for this enumeration type [-Wenum-constexpr-conversion]
/var/tmp/portage/dev-qt/qtlocation-5.15.10/work/qtlocation-everywhere-src-5.15.10/src/3rdparty/mapbox-gl-native/deps/boost/1.65.1/include/boost/mpl/aux_/static_cast.hpp:24:47: note: 
      expanded from macro 'BOOST_MPL_AUX_STATIC_CAST'
#   define BOOST_MPL_AUX_STATIC_CAST(T, expr) static_cast<T>(expr)
                                              ^