[llvm] [Debuginfo][TailCallElim] Fix #86262: drop the debug location of entry branch (PR #86269)

[Stephen Tozer via llvm-commits]

https://github.com/SLTozer commented:

A couple more inline comments about the test - if it turns out the test isn't needed it can be deleted, but if it's adding unique coverage then LGTM.

https://github.com/llvm/llvm-project/pull/86269