Gitian: refresh the stale Monero dir via --setup switch

[mj-xmr]

Prevents symptoms such as:

Submodule 'external/miniupnp' is not up-to-date.

during performing "Reproducible Builds".

A much less obtrusive alternative to #8292

Here I'm simply deleting the monero directory via the --setup switch and allow it to be cloned from scratch.
Thanks to @hyc for pointing out the easy way.

[jeffro256]

Ah, the good ole "turn it off and turn it back on" :)

Where are the submodules populated in this script, and could you simplify the script by adding --recursive when cloning monero repo?

[mj-xmr]

Where are the submodules populated in this script, and could you simplify the script by adding --recursive when cloning monero repo?

Unfortunately the problem is, that they're (re-)populated in the gitian-build project, effectively overwriting what you'd do here, like you can see in #8292 . That project is out of our control and patching it like I did, requires a leap of faith form the Reviewers/Users.

Even though it sounds ok for the gitian-build to download the subs, the script doesn't properly synchronize them, after we update our references in Monero to the new versions of the submodules.

[jeffro256]

Ah, which was why you changed the gitian repo URL in the other PR, makes sense. It seems like Bitcoin Core plans on sunsetting gitian-build in favor of GUIX, so maybe we will have to maintain our own gitian anyways sometime in the future. At any rate, I like this solution much better.

[mj-xmr]

@jeffro256 : Resolved conflicts