bin/dotc silently ignores build failure

[olafurpg]

Following the steps in getting started guide, I get the following error:

$ ./bin/dotc tests/pos/HelloWorld.scala
The script is going to build the required jar files
Building dotty-interfaces...
done
Building dotty...
done
Building tests...
done
New files detected in dotty, rebuilding...
done
New files detected in dotty-tests, rebuilding...
done
Error: Could not find or load main class dotty.tools.dotc.Main

Running sbt compile I get a unresolved dependency on jline. After fixing the dependency issue, I was able to run bin/dotc without issues.

I would like bin/dotc to give a more useful error message when the build fails.