To build Bazel from source in an environment where you don't want to use any Internet binaries, you need a Java built from source. Needing a Java is painful. You also need a Bazel to build Bazel.

And Bazel's build system itself IIRC wants to download stuff from the Internet on build - which can be pre-fetched, but distro maintainers still don't like having to deal with taht.

This is nonsense building OpenJDK from source should be as easy as:

    bash configure && make images

Edit: never mind, I think I was confused what the comment was saying.

Look at what Nix or Guix would have to do to build a project using Bazel vs a project using CMake.