hadrian: Reduce verbosity on failed testsuite run
When the testsuite failed before it would print a big exception which gave you the very long command line which was used to invoke the testsuite. By capturing the exit code and rethrowing the exception, the error is must less verbose:
Error when running Shake build system:
at want, called at src/Main.hs:104:30 in main:Main
* Depends on: test
* Raised the exception:
user error (tests failed)