Update bindgen rules to build clang from source.

[UebelAndre]

This change updates the default rust_bindgen rules to build libclang and clang from source using the Bazel rules sourced in the llvm-project repository for use in RustBindgen actions. The version of Clang that Bindgen uses by default is updated 14.0.6 which was what I was able to get building.

Some breaking changes include:

• Users must now load one extra bzl file if they don't already have have llvm-project defined in their WORKSPACE.

load("@rules_rust//bindgen:transitive_repositories.bzl", "rust_bindgen_transitive_dependencies")

rust_bindgen_transitive_dependencies()

• rust_bindgen_repositories is deleted as a means of forcing users to take a look at the updated dependencies.

closes #919

[8573]

Is there an option not to build Clang from source, for users who don't need that?

[UebelAndre]

You should still be able to register your own toolchains

[UebelAndre]

Is there an issue you’re running into building clang from source?

[aaronmondal]

@UebelAndre Cool change! I want to integrate bindgen-similar functionality between rules_ll and rules_rust via the cxx crate and with this change I can test interop with our bzlmod variant for LLVM.

For reference, LLVM/bzlmod in rules_ll looks like this: https://github.com/eomii/rules_ll/blob/bdd243466d7c5e8be8a9d7f7fcb179b2a1ae084b/MODULE.bazel#L25-L50.

The upstream patch is at https://reviews.llvm.org/D137008. I'll double-check that things are compatible with the usage in rules_rust when I find time to revise that patch.