Add timeout to version.py execution

[m-reuter]

version.py with --sections allhangs on google collab. see #699

Possible solutions:

• to not call all section, but e.g. only "+git"
• to fix whatever is hanging in version.py (if that is even possible as maybe the pip stuff is too slow on collab or the md5 computation)
• put a timeout to ensure that the background process is terminated eventually (this is what I do here as a quick fix)

[dkuegler]

There are technically 3 components to version, pip, git, and checkpoints. ... I think instead of adding a timeout to the version call altogether. It would be better to add timeouts to the individual components internally (as those are mostly calls to binaries, e.g.. git, md5 or pip).

This version would not generate the build file at all I believe, but incomplete build files should be much preferred...