main ant/maven build). Use this only for actions that do actual building.
Any prepartion of the source code should be done using 'init' or 'prebuild'.
+Any building that takes place before build= will be ignored, as either ant,
+mvn or gradle will be executed to clean the build environment right before
+build= (or the final build) is run.
+
You can use $$SDK$$, $$NDK$$ and $$MVN3$$ to substitute the paths to the
android SDK and NDK directories, and maven 3 executable respectively.