swr: [rasterizer core] clang override for _mm_undefined*
swr: [rasterizer core] clang override for _mm_undefined*

Not supported in older xcode versions.

Reviewed-by: Bruce Cherniak <a5345730962d952f474b19e983398300e1cb5f29@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler