Darwin: use the correct include for locale functions (#1987)

Fixes #1973

Signed-off-by: L. E. Segovia <amy@amyspark.me>
Co-authored-by: Doug Walker <doug.walker@autodesk.com>

Author: amyspark

src/utils/NumberUtils.h

@@ -11,9 +11,12 @@
 #endif
 
 #include <cstdlib>
+#ifdef __APPLE__
+#include <xlocale.h>
+#else
 #include <locale>
+#endif
 #include <system_error>
-#include <type_traits>
 
 namespace OCIO_NAMESPACE
 {