[llvm] build_llvm_release.bat: Remove multiple ninja calls (PR #218702)

[Hans Wennborg via llvm-commits]

https://github.com/zmodem approved this pull request.

Yes, this was for flaky tests and flaky builds.

In particular, on my machine mt.exe would often fail to update a file right after linking, due to corporate antivirus getting in the way, which could break both regular builds and check-targets.

The consecutive ninja invocations was a hacky way to handle that, but if this is not an issue on the CI, removing them sounds good to me.

https://github.com/llvm/llvm-project/pull/218702