Update README.

README.md

@@ -15,6 +15,13 @@ designed specifically with mass-scale Minecraft in mind.
   may work, but we make every endeavor to support these server implementations
   specifically.)
   
+## Building
+
+Velocity is built with [Gradle](https://gradle.org). We recommend using the
+wrapper script (`./gradlew`) as our CI builds using it.
+
+It is sufficient to run `./gradlew build` to run the full build cycle.
+
 ## Status
 
 Velocity is far from finished, but most of the essential pieces are in place: