Design a best practice for putting "change #" in an output filename

Paraphrased from #291

We have rules internally in vmware that put "change numbers" in file names. Some observations from experience
- this is error prone on CI systems that do incremental builds. Changing file names will cause files to accumulate over time, filling up disk space.
- if some piece of CI does not know the parameter passed into the build it may have to heuristically choose the "latest" file found with a glob. Which make me :( .

We have been batting around the idea of "pkg_install" that would produce an "install script" that would copy (or link) from bazel-out file locations derived from targets to a directory outside of bazel-out, renaming as it goes. Ideally the pkg_install script would be the only place that would need to know about command line parameters that change file names and we would not need this capability on all of the pkg_* rules.

@mzeren-vmw @nacl