[llvm] llvm-reduce: Preserve original callsite calling conv when removing arguments (PR #133411)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Mar 28, 12:49 PM EDT**: [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/133411) rebased this pull request as part of a merge.


https://github.com/llvm/llvm-project/pull/133411