This picks up a newer version of LLVM and the LLVM Bazel integration.
The big change here is that we can configure the LLVM targets that are
built, which allows us to dramatically reduce the build costs by
focusing on a couple of CPUs for the time being.
There are a few API updates needed as well.
This also rotates the cache version so we start with a clean Bazel cache
from here. Otherwise we'd potentially pay the cost of carrying around
stale bits of LLVM endlessly.
What this does:
- Sets up a `migrate_cpp` tool which currently only runs `clang-tidy`.
- This is intended to have more transformations in the future.
- Sets up a `migrate_cpp.sh` script.
- This copies the original woff2 code into a `carbon` directory and runs the `migrate_cpp` tool on it there.
- Adds the initial `carbon` directory of woff2
- To be clear, this is currently only updated via `clang-tidy`.
- More transformations should be expected in the future.
- Minor related edits. For example:
- Adjust pre-commit to skip the `carbon` directory, because it's third-party code and shouldn't be edited in the same way.
- Adds `@brotli_carbon` as a local repository so that we can "build" outputs.
- Makes clang-tidy from the bootstrap toolchain accessible for BUILD dependencies, as it's then used for `migrate_cpp`.
What this does not do:
- Any actual transformation of C++ code to Carbon
Co-authored-by: Matthew Riley <mdriley@gmail.com>
Chandler Carruth
Jon Meow
