[compiler-rt] [compiler-rt][XRay] Make `xray_interface.h` C compliant (PR #140068)

[Jan André Reuter via llvm-commits]

Thyre wrote:

> LLVM Buildbot has detected a new failure on builder `clang-ppc64le-linux-test-suite` running on `ppc64le-clang-test-suite` while building `compiler-rt` at step 6 "test-build-unified-tree-check-all".
> 
> Full details are available at: https://lab.llvm.org/buildbot/#/builders/95/builds/13758
> Here is the relevant piece of the build log for the reference

The test failure seems to be related to a missing `libstdc++`, though I have currently absolutely no idea why it works on other machines then. I would've expected to see this before merging as well. I'm not able to reproduce this on my machine, though it is not a `ppc64le` one.

https://github.com/llvm/llvm-project/pull/140068