Built SDL2_image and _mixer static

libsdl2_mixer/external/flac-1.3.2/m4/add_cflags.m4

@@ -0,0 +1,18 @@
+dnl @synopsis XIPH_ADD_CFLAGS
+dnl
+dnl Add the given option to CFLAGS, if it doesn't break the compiler
+
+AC_DEFUN([XIPH_ADD_CFLAGS],
+[AC_MSG_CHECKING([if $CC accepts $1])
+	ac_add_cflags__old_cflags="$CFLAGS"
+	CFLAGS="$1"
+	AC_TRY_LINK([
+			#include <stdio.h>
+			],
+		[puts("Hello, World!"); return 0;],
+		AC_MSG_RESULT([yes])
+			CFLAGS="$ac_add_cflags__old_cflags $1",
+		AC_MSG_RESULT([no])
+			CFLAGS="$ac_add_cflags__old_cflags"
+		)
+])# XIPH_ADD_CFLAGS