feat!: 'support' git submodules when cloning a repository

This is the bare minimum dumbest possible thing that could possibly work.

Nota Bene: this feature is not robust against 'abuse' by multiple modules trying to build the 'same' bundled libraries and then install the result into the configured kdedir.
Such modules will end up overwriting each other's artifacts and you get to keep the pieces.
2 jobs for submodule-spray-and-pray in 2 minutes and 31 seconds (queued for 67 minutes and 10 seconds)
Status Job ID Name Coverage
  Test
passed #80305
smoke-test

00:01:56

passed #80304
unit-test

00:00:34