[Bazel] Make `builtin_headers_gen` as subset of CMake's `clang-resource-headers`

At the moment, two files are not installed by CMake.

- `lib/Headers/openmp_wrappers/time.h`
- `lib/Headers/ppc_wrappers/nmmintrin.h`

`builtin_headers_gen` is available as the source of rules_pkg.
The difference of the layout of installed headers makes cache hit harder.