[llvm] Avoid exposing password and token from git repositories (PR #105220)

[Danila Malyutin via llvm-commits]

danilaml wrote:

@tuliom the error is triggered in certain configs/machines we use but
1) we do not use anything that'd require `LLVM_REPOSITORY` define so those configs were not affected anyway
2) using `-DLLVM_FORCE_VC_REPOSITORY` to override the error unsets `LLVM_REVISION` which is actually used by llvm.

https://github.com/llvm/llvm-project/pull/105220