When flattening global structs for MSL, don't qualify names of built-in members.
When flattening global structs for MSL, don't qualify names of built-in members.

KhronosGroup/SPIRV-Cross,h3xl3r/SPIRV-Cross,KhronosGroup/SPIRV-Cross,h3xl3r/SPIRV-Cross,h3xl3r/SPIRV-Cross,KhronosGroup/SPIRV-Cross,h3xl3r/SPIRV-Cross,h3xl3r/SPIRV-Cross,KhronosGroup/SPIRV-Cross,KhronosGroup/SPIRV-Cross,KhronosGroup/SPIRV-Cross