[gcc(refs/users/aoliva/heads/testme)] [libstdc++] add _GLIBCXX_CLANG to workaround predefined __clang__

https://gcc.gnu.org/g:1472684e8baaf4137c27fc725e6f2b1e852b commit 1472684e8baaf4137c27fc725e6f2b1e852b Author: Alexandre Oliva Date: Fri May 31 09:10:55 2024 -0300 [libstdc++] add _GLIBCXX_CLANG to workaround predefined __clang__ A proprietary embedded operating system

[gcc(refs/users/aoliva/heads/testme)] [libstdc++] add _GLIBCXX_CLANG to workaround predefined __clang__

https://gcc.gnu.org/g:68673b6784aa74e7209e8d54c35124799c0c8fc4 commit 68673b6784aa74e7209e8d54c35124799c0c8fc4 Author: Alexandre Oliva Date: Fri May 31 09:10:55 2024 -0300 [libstdc++] add _GLIBCXX_CLANG to workaround predefined __clang__ A proprietary embedded operating system