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

[via llvm-commits]

================
@@ -510,7 +510,9 @@ void TailRecursionEliminator::createTailRecurseLoopHeader(CallInst *CI) {
   NewEntry->takeName(HeaderBB);
   HeaderBB->setName("tailrecurse");
   BranchInst *BI = BranchInst::Create(HeaderBB, NewEntry);
----------------
mikaelholmen wrote:

BI is unused now (but referenced in the comment at line 515), leading to compiler warnings.
```
../lib/Transforms/Scalar/TailRecursionElimination.cpp:512:15: error: unused variable 'BI' [-Werror,-Wunused-variable]
  BranchInst *BI = BranchInst::Create(HeaderBB, NewEntry);
              ^
1 error generated.
```

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