FindOpenMP: Broken with keg-only homebrew libomp
In latest homebrew libomp is keg-only, which means it was not symlinked into /usr/local, because it can override GCC headers and result in broken builds.
This results in FindOpenMP not finding anymore omp.h and libomp.dylib for the Apple clang compiler in /usr/local/opt/libomp/include and lib. We would need an OpenMP__CXX_LIB_DIR input hint to specify where to find the library. The existing input hint OpenMP__CXX_INCLUDE_DIR is only used after the library is found, but that one is never found.
Edited by Brad King