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

[Rainer Orth via llvm-commits]

rorth wrote:

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

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