[gtk/wip.win32.fixes: 345/347] meson.build: Improve F16C detection on Visual Studio

[Chun-wei Fan <fanchunwei src gnome org>]

commit 184f034061d5423e093d44be2814d570d9b917ad
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Mon Apr 12 16:24:37 2021 +0800

    meson.build: Improve F16C detection on Visual Studio
    
    The __builtin_cpu...() intrisics are strictly for GCC/CLang-based compilers, so
    don't use them in the checking code on Visual Studio.  The test code will still
    compile without this change, but will certainly fail if we want it to link.

 meson.build | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/meson.build b/meson.build
index 641208158c..902bd72031 100644
--- a/meson.build
+++ b/meson.build
@@ -707,8 +707,10 @@ int main () {
   __m128i i = _mm_cvtps_ph (s, 0);
   _mm_storel_epi64 ((__m128i*)h, i);
 
+#if defined (__GNUC__) || defined (__clang__)
   __builtin_cpu_init ();
   __builtin_cpu_supports ("f16c");
+#endif
 
     return 0;
 }'''