Built SDL2_image and _mixer static

libsdl2_mixer/external/libvorbis-1.3.5/m4/add_cflags.m4

@@ -0,0 +1,15 @@
+dnl @synopsis AC_ADD_CFLAGS
+dnl
+dnl Add the given option to CFLAGS, if it doesn't break the compiler
+
+AC_DEFUN([AC_ADD_CFLAGS],
+[AC_MSG_CHECKING([if $CC accepts $1])
+	ac_add_cflags__old_cflags="$CFLAGS"
+	CFLAGS="$CFLAGS $1"
+	AC_TRY_LINK([#include <stdio.h>],
+		[puts("Hello, World!"); return 0;],
+		AC_MSG_RESULT([yes]),
+		AC_MSG_RESULT([no])
+		CFLAGS="$ac_add_cflags__old_cflags")
+		])
+])# AC_ADD_CFLAGS