util: Add ATTRIBUTE_OPTIMIZE(flags)

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30622>

meson.build

@@ -1044,6 +1044,7 @@ endforeach
 _attributes = [
   'const', 'flatten', 'malloc', 'pure', 'unused', 'warn_unused_result',
   'weak', 'format', 'packed', 'returns_nonnull', 'alias', 'noreturn',
+  'optimize',
 ]
 foreach a : cc.get_supported_function_attributes(_attributes)
   pre_args += '-DHAVE_FUNC_ATTRIBUTE_@0@'.format(a.to_upper())