Merge cherrypicks of [1167933, 1167888] into ndk-release-r21

Change-Id: I28aeaaf04adf1441482a0dbfa05c770adbd5972e
diff --git a/Android.mk b/Android.mk
index 6b9b80f..0cad257 100644
--- a/Android.mk
+++ b/Android.mk
@@ -28,8 +28,6 @@
 
 define gen_libshaderc
 
-$(1)/libshaderc.a: $(SHADERC_HEADERS_IN_OUT_DIR)
-
 $(1)/combine.ar: $(addprefix $(1)/, $(ALL_LIBS))
 	@echo "create libshaderc_combined.a" > $(1)/combine.ar
 	$(foreach lib,$(ALL_LIBS),
@@ -59,4 +57,6 @@
 
 endef
 
+libshaderc_combined: $(SHADERC_HEADERS_IN_OUT_DIR)
+
 $(eval $(call gen_libshaderc,$(TARGET_OUT),$(TOOLCHAIN_PREFIX)))