Adding PHONY target for ios and android in native build.

native-builds/Makefile

@@ -6,7 +6,11 @@ DEPOT_TOOLS_TAG=3add4b62b8fc420ba5a6cc0c8bddcf152c00a970
 
 NATIVE_SKIA_ROOT=../skia
 
-all: ios/libskia_core.a
+all: ios
+
+ios: ios/libskia_core.a
+
+
 
 ios/libskia_core.a: depot_tools/README
 	mkdir -p ios/i386
@@ -49,4 +53,6 @@ depot_tools/README:
 	touch $@
 
 clean :
-	rm -rf depot_tools ios
+	rm -rf depot_tools ios
+
+.PHONY: all clean ios android