Check doc comments when you run update-api.

Bug: 14614668
Change-Id: I7ae8de19b51aeaeef70e2ba8bfa268ec70dfaf64
diff --git a/Android.mk b/Android.mk
index c80a9ab..beee726 100644
--- a/Android.mk
+++ b/Android.mk
@@ -720,8 +720,9 @@
 $(full_target): $(framework_built) $(gen)
 
 # Run this for checkbuild
-.PHONY: checkbuild
 checkbuild: doc-comment-check-docs
+# Check comment when you are updating the API
+update-api: doc-comment-check-docs
 
 # ====  static html in the sdk ==================================
 include $(CLEAR_VARS)