Reduce a bit of the soul-crushing log spam created by buildkite

[andralex]

First, the default git clone will output progress message every percent of the way, which is not useful for offline log inspection.

Second, buildkite uses the --- prefix to group log output. However, that's not nested so calling the cloning script will group things the wrong way. So I added those echos to distinguish cloning from building.

Related: isn't it excessive to output every single command run? I'd understand doing so temporarily for debugging (and even in that case I'd argue well-thought logging would be vastly better), but to leave it on by default seems much.

[maxhaton]

LGTM

[andralex]

@maxhaton thanks! Is that script deployed automatically?

[Geod24]

Yes it is.