(macOS) Set up CROSS_COMPILE for ARM 64bit

Makefile

@@ -47,7 +47,17 @@ else ifeq ($(platform), osx)
 	SHARED := -dynamiclib
 	OSXVER = `sw_vers -productVersion | cut -d. -f 2`
 	OSX_LT_MAVERICKS = `(( $(OSXVER) <= 9)) && echo "YES"`
-	fpic += -mmacosx-version-min=10.1
+   ifeq ($(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)
+		CPPFLAGS += $(TARGET_RULE)
+		CXXFLAGS += $(TARGET_RULE)
+		LDFLAGS  += $(TARGET_RULE)
+   endif
 
 # iOS
 else ifneq (,$(findstring ios,$(platform)))