git package missing from build VM images

[Evan]

https://sentry.io/canonical-ao/snapcraft/issues/757489565

Running `snapcraft --debug` and `apt install git` fixes the issue.

[Sergio Schvezov (sergiusens)]

git is autoinstalled by snapcraft if operating on git sources (with source: . then source-type: git might be needed but only if you are going to run git commands).

This is debatable as git is not necessarily going to be preinstalled on the builders and installed as a side effect of the source type. What this needs however is a proper error response.

[Kyle Fazzari (kyrofa)]

The error here is because `version: git` is being used, and snapcraft doesn't add git to build-packages unless a git source is used. Snapcraft should probably add git to build-packages if `version: git` is used.

[Evan (ev)]

Thanks Kyle and Sergio.

Confirmed that adding `source-type: git` to a part convinces snapcraft to pull in git. I'm +1 on doing this automatically when `version: git` is set.

[Sergio Schvezov (sergiusens)]

https://github.com/snapcore/snapcraft/pull/2403

[Sergio Schvezov (sergiusens)]

https://github.com/snapcore/snapcraft/pull/2406