If a multiproject has a rootProject, then
gradle install places an empty (classless) JAR in .m2, even though build/libs/myproject-version.jar does have classes.
One workaround involves moving the rootProject to a “…-common” child project, but it would be better for this to work out of the box.
Gradle 2.3.10 with built-in Maven plugin
Mac OS X 10.11.4 El Capitan