Suggestion: Change appropriate jenkins jobs to be shallow clones

[ryanaslett]

In researching the disk usage of the jenkins workspace nodes, I noticed that they tend to accumulate a lot of git repositories, and that all of the git repos are full clones of the entire history of the nodejs project.

I haven't fully dug into the depths of everything that happens in the testing pipelines to know whether or not that is a requirement, and whether or not there are jobs that need the full history, so this may not be a palatable change.

The full clones varied from 1.2 to 1.8 gb, and on the one server I looked at, there were about 140 clones on disk from various older builds. A depth 1 shallow clone of the nodejs project is only about 100M, so t would save 150-200GB, which would give a fair amount of breathing room on those 450GB disks.

I couldn't find any previous discussions in the build repo about shallow clones beyond specific jobs (i.e. no "we cant do that because of reason x..) So hopefully this suggestion has some merit.