[compiler-rt] [llvm] Add extendhfxf2 into compiler rt (PR #111099)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> The patch likewise broke the [Solaris/amd64 bot](https://lab.llvm.org/staging/#/builders/120/builds/2975).

Thanks - I pushed a revert for this now.

https://github.com/llvm/llvm-project/pull/111099