[gtk/wip/otte/center-center-center] build: Make sure ifuncs exist when using fp16

[Benjamin Otte <otte src gnome org>]

commit d57b3b5b3c81543d93a3168238c3779a8f9b573e
Author: Benjamin Otte <otte redhat com>
Date:   Fri Oct 22 16:31:40 2021 +0200

    build: Make sure ifuncs exist when using fp16
    
    Fixes gcc compiles on Windows.
    
    Fixes #4285

 meson.build | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/meson.build b/meson.build
index 897de13766..a699580f21 100644
--- a/meson.build
+++ b/meson.build
@@ -712,12 +712,19 @@ if get_option('f16c').enabled()
 # if !defined(__amd64__) && !defined(__x86_64__)
 #   error "F16C intrinsics are only available on x86_64"
 # endif
+#if !defined __has_attribute
+# error "No __has_attribute() support"
+#endif
+#if !__has_attribute(ifunc)
+# error "ifunc not supported"
+#endif
 #endif
 #if defined(__SSE__) || defined(_MSC_VER)
 # include <immintrin.h>
 #else
 # error "No F16C intrinsics available"
 #endif
+
 int main () {
   float f[4] = { 0, };
   unsigned short h[4] = { 0, };