/usr/x86_64-w64-mingw32/include/semaphore.h is in mingw-w64-x86-64-dev 3.1.0-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/x86_64-w64-mingw32/include/../../share/mingw-w64/include/semaphore.h