Errors don't appear to be getting forwarded through the compilerOutputLines as expected

If you for instance compile with `--enable-experiment foobar` I would expect an error message about an unknown experiment. We are notified that there is 1 error, but cannot get any text for it.

Start by reproducing the CLI compile with `--enable-experiment foobar` and tracing how `compilerOutputLines` handles the compiler response. Check why the error count is forwarded without its text. Done means the unknown-experiment message is available through `compilerOutputLines` along with the reported error.

Written by the indexing model from the issue text.