This reverts commit 3e4547f52e7ebec633f8bfefc8a396d944edf908, reversing changes made to 6edf9382bcc1240ad6f97c8b752cfe56cef9965d.
Homebrew's actually ended up using a fair few gems. While we want to avoid Bundler at runtime (and this PR still does that, in fact uses Bundler even less at runtime than it did before) writing our own version to use at build-time seems redundant.
Container::Executable
