openmp library incorrectly assumes OpenPower ELF v2 ABI is only used on little endian systems. This is not true, since ELFv2 ABI supports both big and little.
This patch correct this assumption by checking CALL_ELF variable instead of endiannes, and unbreaks openmp on FreeBSD/powerpc64-ELFv2 port (https://wiki.freebsd.org/powerpc/llvm-elfv2)
*I set the reviewers based on git log. Please feel free to change.