Automatically cleanup dirty llvm repo

[PhilippvK]

When pressing CTRL+C while patches are being applied, it is very likely that the target llvm repo will be in a unclean state. To resolve this, users have to run git restore . and git clean -f . manually which should be avoided in the future.

The main problem with automating this is the risk of accidentally dropping any manually made changes. Further, in an unlucky scenario, it could remove the .seal5 meta dir, which is not desirable...

In interactive mode, we could just ask the user if the cleanup should really be applied.