build-tools Phase 2

Like #44 (closed) but for build-tools

Current plan is to just do the work in platform-tools, copy it over, and then apply the same thing here to components aren't present there.

1. Wait for platform-tools phase 2 step 1 to be done.
2. Get rid of any internal-only dependencies This will basically include any package which does not provide a binary, since all the libraries were only-intended for internal use. We need to verify rdepends though before going through this.
3. Figure out a tag / branch to update this to, something that's used to build the upstream build-tools 29.0.x