Now that the Windows installer no longer does anything besides self-extract, maybe it would make sense to distribute the toolchain as a plain zip file instead, or in addition to the current installer?
I'm not familiar with this script, but rather than "create installer, then unpack it, remove some stuff, repack" would it make more sense to have "create archive with just the stuff we want to be in the archive, then unpack that and add files we need for installer" as the overall flow?
Then you could also use the "7za" executable, which I believe has fewer deps (at least it was easier to use in chromium/win cross builds).
I think there's no easy way to do the "add files we need for installer" step though. The installer is generated with a lot of cmake, so it's easier to do it in this order.
Getting CMake to make the zip archive would be nice, but it's not a requirement.
I think it could, but not in the same build where it's configured to create the nsis installer. Repacking like this saves a lot of time.