V2 post-processing step leaves "fragments" directories

[bshaffer]

This is of course very low priority, as it does not cause any issues AFAIK, but when untar-ing the resulting package from the GAPIC post-processor, I can see that the fragment directories are there even though they contain no files (and we don't want them there):

$ bazel build google/cloud/support/v2:google-cloud-support-v2-php
$ tar -xvf bazel-bin/google/cloud/support/v2/google-cloud-support-v2-php.tar.gz
google-cloud-support-v2-php/fragments/
google-cloud-support-v2-php/fragments/Google/
google-cloud-support-v2-php/fragments/Google/Cloud/
google-cloud-support-v2-php/fragments/Google/Cloud/Support/
google-cloud-support-v2-php/fragments/Google/Cloud/Support/V2/
google-cloud-support-v2-php/proto/
...

We should remove the empty directories in the post processing step to reduce the noise

[noahdietz]

The fragment files are excluded here, but the directories aren't removed. Tricky! Thanks, should be excluded for sure. Does this block generation? Is owlbot able to ignore those?

[bshaffer]

Owlbot does not move these over, and even if they did, git doesn't track empty directories, so this doesn't block anything