add possibilty to open dired in `work` directory directly for ebuild-mode output

Hi, thanks for setting the jit things up so I can install this. I works like a charm now.

I often have the problem that I only do a ebuild blaba prepare (using ebuild-run-command from ebuild-mode) to get the patched sources of a package to write another patch for it. I this case I wont have an error to use to go to the working directory (usually something like /var/tmp/portage/category/packagename/work) and I will have to type out this lang patch in helm-find-file.

Could we have a function that goes to the working directory directly from the ebuild-run-command output? Like firing up a dired buffer set to this path.