[Clang] Add `__CLANG_GPU_DISABLE_MATH_WRAPPERS` macro for offloading math (#98234)

Summary:
Currently we replace all math calls with vendor specific ones. This
patch introduces a macro `__CLANG_GPU_DISABLE_MATH_WRAPPERS` that when
defined will disable this.

I went this route instead of a flag for two reasons. One, I think we
have too many flags as is, and we already have `-nogpuinc` to cover
disabling these wrappers entirely, so this would be a really specific
subset of that. Second, these math headers aren't easily decoupled by
simply not including a single header from the clang driver layer.
There's the cmath and the regular math forward declares it would disable
as well.

Note, this currently causes errors because the GPU `libm` doesn't have
`powi`, that's an NVIDIA extension I'll add to LLVM libm.
3 files changed
tree: 1f38130b113a7f221805600e298475819b7defb7
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. libc/
  11. libclc/
  12. libcxx/
  13. libcxxabi/
  14. libunwind/
  15. lld/
  16. lldb/
  17. llvm/
  18. llvm-libgcc/
  19. mlir/
  20. offload/
  21. openmp/
  22. polly/
  23. pstl/
  24. runtimes/
  25. third-party/
  26. utils/
  27. .clang-format
  28. .clang-tidy
  29. .git-blame-ignore-revs
  30. .gitattributes
  31. .gitignore
  32. .mailmap
  33. CODE_OF_CONDUCT.md
  34. CONTRIBUTING.md
  35. LICENSE.TXT
  36. pyproject.toml
  37. README.md
  38. SECURITY.md
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