Makefile: ensure that schema source files are in place before schema recompilation occurs - #2257

Ok, my apologies: I definitely should have tested this before opening a pull request.

From attempting the build process locally: it seems that in fact the install_schemas step is intended to occur before compile_schemas -- the latter requires that the files have already been written to the $(SCHEMA_DIR) directory.

I've moved this back into 'draft' pull request status while confirming more of the details.

It probably is worth adding a reno entry for this after all.. this race condition can be a source of build nondeterminism, and that means that some downstream packagers might have added -j1 or potentially even infrastructure-level workarounds to prevent guake building in parallel environments. So an informational message in the changelog could help as a hint that it should be OK to remove those workarounds.

cc @Davidy22 - I made a bit of a mess developing this PR - my apologies for not testing this until after I opened it - but I believe that it is ready now and resolves a genuine build-time race condition for guake.

Sorry about the delay in checking the build, and seems like github did some deprecating in the time between your testing and me checking this. I could do that seperately and you could pull, or you could bump the version for the upload-artifact action in your tree to v4

Thanks for running the CI checks and taking a look! I generally prefer to keep changes like those separate, so if that's OK with you, I'll wait until that is resolved and then will rebase/pull.

Alright, there's still some things to resolve with CI but it should be in a state where you can update your branch and checks here should pass.

Somewhat-delayed reply: thank you @Davidy22!