(Mac) Add cross-compilation for arm64

Makefile

@@ -104,7 +104,14 @@ ifeq ($(arch),ppc)
 endif
    OSXVER = `sw_vers -productVersion | cut -d. -f 2`
    OSX_LT_MAVERICKS = `(( $(OSXVER) <= 9)) && echo "YES"`
+ifeq ($(OSX_LT_MAVERICKS),YES)
    fpic += -mmacosx-version-min=10.1
+endif
+   ifeq ($(CROSS_COMPILE),1)
+	TARGET_RULE   = -target $(LIBRETRO_APPLE_PLATFORM) -isysroot $(LIBRETRO_APPLE_ISYSROOT)
+	CFLAGS   += $(TARGET_RULE)
+	LDFLAGS  += $(TARGET_RULE)
+   endif
 
 # iOS
 else ifneq (,$(findstring ios,$(platform)))