Make the sbt scripted tests use the caching resolver
Make the sbt scripted tests use the caching resolver

The CI is setup to have
https://github.com/lampepfl/dotty-drone/blob/master/dotty-docker/repositories
as ~/.sbt/repositories to avoid hitting sonatype when an artifact is not
present in the local cache, the sbt scripted tests were not respecting
that setting so far because they use a different sbt boot directory.

som-snytt/dotty,sjrd/dotty,som-snytt/dotty,som-snytt/dotty,dotty-staging/dotty,lampepfl/dotty,dotty-staging/dotty,lampepfl/dotty,lampepfl/dotty,sjrd/dotty,lampepfl/dotty,dotty-staging/dotty,dotty-staging/dotty,som-snytt/dotty,sjrd/dotty,sjrd/dotty,som-snytt/dotty,sjrd/dotty,lampepfl/dotty,dotty-staging/dotty