I was setting up a Gradle-based Android project on Jenkins today.  I had read in a few places that Gradle would be downloaded somehow after installing the corresponding plugin but the build was failing within seconds of starting.  My SDK was fully up to date and I had already set ANDROID_HOME but the build was still complaining about not being able to find gradlew.  

When I read the manual I discovered that gradlew, gradlew.bat (for our Windows friends) and the gradle/ directory in the project’s root are supposed to be committed to source control.  The next build went beautifully smoothy!