Consider adding include-what-you-use to clang package

irods could benefit from usage of include-what-you-use, but IWYU is very closely tied to the version of clang it is built against. since it can be [built as part of LLVM](https://github.com/include-what-you-use/include-what-you-use/tree/clang_16?tab=readme-ov-file#how-to-build-as-part-of-llvm), let's consider adding it to our clang package.