Can't skip locker: master doesn't build with starr currently
Build docs during pr-scala-test.

TODO: split into parallel jobs

Will still need to build pack first,
then pass it to test.pos_neg | test.run | docs
temporarily disables scala/scala tests for push a new build of paradise 2.11
Revert "temporarily disables scala/scala tests for push a new build of paradise 2.11"

This reverts commit 47d7d5f77981b1f31f22b532ec6ac060b100a98a.
fixes paradise breakage for 2.11.0-SNAPSHOT
Don't rebuild core when already on maven.

PR validation can be retried with PLS REBUILD.
As our artifactory does not allow overwriting snapshots,
rebuilds would fail if artifacts are already published.

With this tweak, PLS REBUILD works and is faster to boot!
checkAvailability changes working directory

So, do a `cd $WORKSPACE/scala/` after.
Wipe org/scala-lang part of m2repo.

Since we download a new set of Scala jars for each validated commit,
build nodes quickly run out of disk space unless you wipe this.

uber-build's m2repo is in `$WORKSPACE/target/m2repo`,
our own m2repo is in `$WORKSPACE/m2repo` -- TODO: align
To revert: Use adriaanm/uber-build until PR is merged.

PR: https://github.com/scala-ide/uber-build/pull/19