Fix Mac build by using prebuilt SDL library for OS X

Change-Id: I60657e72b13f9425d642b6b5dd770ce4ecd66abd
diff --git a/Makefile.android b/Makefile.android
index 5519896..dd1cd38 100644
--- a/Makefile.android
+++ b/Makefile.android
@@ -324,6 +324,9 @@
 ifeq ($(QEMU_HOST_TAG),linux-x86)
     BUILD_SDL_FROM_SOURCES := false
 endif
+ifeq ($(QEMU_HOST_TAG),darwin-x86)
+    BUILD_SDL_FROM_SOURCES := false
+endif
 ifneq ($(SDL_CONFIG),)
     BUILD_SDL_FROM_SOURCES := false
 endif