After commit b337c5b1a1757b2abbc90a7c6955d64242861ab9 builds on FreeBSD see 115 instances of
include/windef.h:60: warning: "__fastcall" redefined
which comes from <stdio.h> including <sys/cdefs.h> which in turns has
#define __fastcall __attribute__((__fastcall__))
Simply #undef-ining __fastcall like we do for some other cases already addresses this.