Please Adopt SPIRV-Cross MacOSX fix

[StrongJoshua]

Hi, I believe that shaderc uses SPIRV-Cross, but I wasn't able to find it in any dependency tree. In any case, I recently posted an issue in that repo about a bug, which was fixed (KhronosGroup/SPIRV-Cross#2539).

I cannot tell if this has yet been adopted into the current build of shaderc-rs, but my build continues to fail, so I imagine it has not yet been. I'm not aware of how to perform this update myself, so any help would be appreciated.

Thanks!