In addition to one of the cstdlib fix here – Gentoo building qtgui error – g++-v8/cstdlib:75:15: fatal error: stdlib.h: No such file or directory we were unable to to build “dev-qt/qtwebengine-5.14.1“.
It appeared the problem was a wrong order of header includes just like the cstdlib and if you have used the fix with QMAKE_CFLAGS_ISYSTEM in /usr/lib64/qt5/mkspecs/common/gcc-base.conf you would encounter this error. Revert back the original value in /usr/lib64/qt5/mkspecs/common/gcc-base.conf (and probably it is a good idea to rebuild the entire system with “emerge -e”):
QMAKE_CFLAGS_ISYSTEM = -isystem
and continue the build from the point you’ve stopped with something like:
ebuild /usr/portage/dev-qt/qtwebengine/qtwebengine-5.14.1.ebuild compile ebuild /usr/portage/dev-qt/qtwebengine/qtwebengine-5.14.1.ebuild install ebuild /usr/portage/dev-qt/qtwebengine/qtwebengine-5.14.1.ebuild qmerge rm -Rf /var/tmp/portage/dev-qt/qtwebengine-5.14.1/