[llvm] [llvm] Include LLVM_REPOSITORY and LLVM_REVISION in tool version (PR #84990)

[Justin Bogner via llvm-commits]

bogner wrote:

Making `Support` depend on `llvm_vcsrevision_h` is a very bad idea. After this change a `git commit` basically causes a full rebuild, making incremental development and things like `git bisect` more or less completely unusable.

Try it out - run `ninja llc`, then `git commit --allow-empty -m 'whoops rebuild everything'`, and then run `ninja llc` again. 2100 targets are out of date on my machine. Before this change (or after reverting it), the same rebuilds 4 targets.

We should probably revert this and if you want the feature in production compilers or something make it an explicit opt in.

https://github.com/llvm/llvm-project/pull/84990