Streamline repo scripts

Created by: ollieparanoid

I'm building the packages for the binary repo manually. The repo is enabled by default in pmbootstrap (disable with --mirror-pmOS="") and it is somewhat usable now and it's a big improvement over having no binary packages at all. But it still needs improvements.

• Change pmbootstrap aportgen to generate gcc-aarch64 etc. not for arch=all (9f674675)
• use --strict for building
• improve the building script: don't use pmbootstrap directly, wrap it with a different config and work path, so the same PC can be used for quickly testing a build without messing with the repo
• polish repo build scripts and publish them (done: pmOS-repo-scripts)
• properly delete old packages (#1306)
• use proper repo description with pmbootstrap commit hash
• use -9 compression for gzip packages (new pmbootstrap parameter)
• Firmware packages: download blobs after installation, so we can build firmware packages, too (right now they don't get built) (#797 (closed))
• Some packages will still build despite the same version being on the binary repo (#955 (closed))
• add pmbootstrap build --all to simply build all packages?
• build everything for x86, too (we do have a x86 device now!)
• figure out a good process to (manually) update packages, with maintainers for packages etc?
• set up a postmarketOS version of https://pkgs.alpinelinux.org aka alpine-turbo
• create build logs for every build and upload them somewhere, so they can be linked from alpine-turbo

and finally (future!):

• automatize it completely: whenever a new commit comes in to master, run the build