Update README.md

README.md

@@ -34,3 +34,14 @@ This cmake makro sets up dummy targets in the cmake configuration which call out
 It also parses the `package.xml` to add target dependencies from each `build_depends` tag (subsequently letting you
 sequence builds across repositories).
 
+It also adds a global and package `gradle-clean` target.
+
+```
+> catkin_make
+# Clean a single gradle package
+> cd ~/rosjava/build/rosjava_core
+> make gradle-clean-rosjava_core
+# Clean all gradle packages
+> cd ~/rosjava/build
+> make gradle-clean
+```