Fix compile errors when the '-mf16c' CFLAG is enabled.
Fix compile errors when the '-mf16c' CFLAG is enabled.

Fixes an issue where 'half.hpp' skips the 'immintrin.h' include
statement if '-mf16c' is used.
(which can happen when using '-march=native')

baldurk/renderdoc,baldurk/renderdoc,Zorro666/renderdoc,Zorro666/renderdoc,baldurk/renderdoc,baldurk/renderdoc,Zorro666/renderdoc,Zorro666/renderdoc,baldurk/renderdoc,baldurk/renderdoc,Zorro666/renderdoc,Zorro666/renderdoc