[HIP] Fix libclang_rt.builtins.a not found

[Rbiessy]

Description

Using the compiler from oneAPI's Base Toolkit and the Codeplay AMD plugin fails to compile by default with the error:

ninja: error: '/path/to/intel/oneapi/2024.2.0/compiler/2024.2/lib/clang/19/lib/x86_64-unknown-linux-gnu/libclang_rt.builtins.a', needed by 'lib/libonemkl_sparse_blas_rocsparse.so.0', missing and no known rule to make it

As far as I know this is an issue for all ROC backends. The issue is that the command find_package(HIP) invokes ${HIP_CXX_COMPILER} -print-libgcc-file-name --rtlib=compiler-rt to find the path of a dependency where HIP_CXX_COMPILER is set as CMAKE_CXX_COMPILER by default. This command is meant to be run with HIP's clang++ but when icpx is used the command is outputting a non-existant file.

As the documentation suggests this can be worked around by building intel/llvm which is not user friendly. The second workaround of setting LIBRARY_PATH did not work for me using ROCm 6.1.0 so I am suggesting to remove it.
The suggested solution should be more resilient and does not need any more action from the user as the environment variables HIPROOT or ROCM_PATH should already be set to use the ROC libraries.

Fixes #336

Checklist

All Submissions

• [N/A] Do all unit tests pass locally? This does not affect the tests.
• [N/A] Have you formatted the code using clang-format?

Bug fixes

• [N/A] Have you added relevant regression tests?
• Have you included information on how to reproduce the issue (either in a
  GitHub issue or in this PR)?

[hjabird]

The docs render properly. I had trouble reproducing the clang-rt issue with the develop branch, but the changes in this PR also didn't create any new issues as far as I could tell.

[mkrainiuk]

Looks good to me, thank you.

[npmiller]

@hjabird @mkrainiuk would it be possible to merge this? It looks ready and it's a recurring issue we run into.