Don't run LLVM regression tests without llvm-test.py script.
Don't run LLVM regression tests without llvm-test.py script.

This is a partial revert of r12664. I forgot we still had exclusions on
mac/linux.

TBR=jvoung@chromium.org
BUG=red bots

Review URL: https://codereview.chromium.org/144713006

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@12665 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client