Fix a lit test issue exposed by r290056

The test requests a target which supports cl_khr_gl_msaa_sharing since in test/PCH/ocl_types.h
it tries to enable cl_khr_gl_msaa_sharing. Therefore this test fails on targets not supporting
cl_khr_gl_msaa_sharing, e.g. ppc64, etc.

The fix is to add triple spir-unknown-unknown which supports cl_khr_gl_msaa_sharing.

llvm-svn: 290059