[llvm] ARM: Add missing test coverage for windows frexp libcalls (PR #146690)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Jul 7, 1:05 AM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/146690).


https://github.com/llvm/llvm-project/pull/146690