[llvm] [Bazel][Clang Tidy] Include builtin headers with clang-tidy (PR #67626)

[Arthur Eubanks via llvm-commits]

aeubanks wrote:

```
$ cat /tmp/b.c
#include <stddef.h>
$ bazel-bin/external/llvm-project/clang/clang -fsyntax-only /tmp/b.c
/tmp/b.c:1:10: fatal error: 'stddef.h' file not found
    1 | #include <stddef.h>
      |          ^~~~~~~~~~
1 error generated.
```

`clang` also doesn't work directly from `bazel-bin`. I don't think it makes sense to add in a workaround just for `clang-tidy` if `clang` doesn't even work. I still think this points to wanting a more complete solution where we properly mirror the upstream build directory.

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