Precompile toolchain binaries to avoid issues

[keith]

Sometimes compiling the toolchain binaries causes timeouts on slower CI machines. One way we could avoid this is by vendoring the binaries for the few files we need instead of causing them to be compiled on the fly. This would also solve hermeticity issues with them

https://github.com/bazelbuild/bazel/issues/17437

[brentleyjones]

If we use rules_pkg for our release archive, we can do what rules_xcodeproj is doing: https://github.com/buildbuddy-io/rules_xcodeproj/commit/b1e6c2077e2c0ff99c2f90506d7b4ecc2911af81

[keith]

Nice!