The default USE flags for sys-devel/libomp compile without hwloc. Any programs that can use or rely on OpenMP will fail the pretend phase requirement checks when using clang. The warning provided dictates you compile and install libomp even though it's already compiled and installed. When enabling the hwloc USE flag for libomp, the pretend phase checks pass and the program compiles as normal.
Steps to Reproduce:
1.compile libomp with default flags
2.try to compile libraw using clang
3.libraw pretend phase fails
* OpenMP support in sys-devel/clang is provided by sys-libs/libomp.
* ERROR: media-libs/libraw-0.20.0::gentoo failed (pretend phase):
* Active compiler does not have required support for OpenMP
Created attachment 655186 [details]
Created attachment 655188 [details]
libraw success with libomp +hwloc