Support overrides for android_app

Test: use it
Change-Id: I61b933b757081f08a417e66a8c02d62916bd3f8b
diff --git a/java/androidmk.go b/java/androidmk.go
index 04e92c9..544322e 100644
--- a/java/androidmk.go
+++ b/java/androidmk.go
@@ -232,6 +232,9 @@
 				}
 
 				fmt.Fprintln(w, "LOCAL_CERTIFICATE :=", app.certificate.pem.String())
+				if len(app.appProperties.Overrides) > 0 {
+					fmt.Fprintln(w, "LOCAL_OVERRIDES_PACKAGES := "+strings.Join(app.appProperties.Overrides, " "))
+				}
 			},
 		},
 	}