[llvm] build_llvm_release.bat: add tarball export to x64 release (PR #79840)

[via llvm-commits]

https://github.com/zmodem commented:

Apologies for the delay, this got buried in my inbox.

Thanks for sending the PR! People keep asking for this, so I think it's worth a try if people think it's useful.

I tried your patch and ended up with a 936 MB .tar.xz file :) Uncompressed it's 4.4 GB.

.tar.xz is perhaps an unusual choice on Windows. On the other hand, a zip file would be much larger. I tried with 7zip's "maximum" setting and got a 1.34 GB file. (With "ultra" it's 1.33 GB so that doesn't seem worth it.)
Do you think users would prefer a zip file even though it's a bit bigger?

https://github.com/llvm/llvm-project/pull/79840