[llvm] [Release] Pass -n to gzip so the release tarball is reproducible (PR #216533)

[Tom Stellard via llvm-commits]

tstellar wrote:

We don't really use this script any more, but I guess this is fine, but can you fix up the commit message?  It would be better if we just re-used the commit message from the AMD commit.

https://github.com/llvm/llvm-project/pull/216533