[clang-tools-extra] [flang] [compiler-rt] [llvm] [clang] [Bazel][Clang Tidy] Include builtin headers with clang-tidy (PR #67626)

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jathu wrote:

@aeubanks @rnk 

> issues with 2: relies on bazel paths, i.e. this puts the symlink at bazel-bin/external/llvm-project/clang-tools-extra/ which happens to be two directories up from bazel-bin/external/llvm-project/clang-tools-extra/clang-tidy/clang-tidy

I also think this is weird, however this seems to be the location clang-tidy expects the headers to be located. This symlink approach was the least intrusive solution I can think of without modifying the overlay logic.

> my worry about baking in the resource dir for the bazel build is that it'll be tied to the bazel build directory structure implementation details, so it's likely that you can't copy the binaries around and create a toolchain out of it

Maybe I'm misunderstanding your point — since these headers are included in the runfiles of the binary, if we do a copy/package the binary, the runfiles will be bundled with the binary. If there is a solution to bundle the headers *within* the binary, that would be great, but I think that goes beyond the goal of this diff.

https://github.com/llvm/llvm-project/pull/67626