Wrap files in bin/ and sbin/ with the location of the gem itself and the
location of any other gems in use (GEM_PATH). This ensures that the bin files
will run with the right environment when executed.
It does however mean that native-inputs will also get wrapped up in any
binaries, which is not good, as it increases the size of the closure, and
risks this code being used at runtime.
* guix/build/ruby-build-system.scm (wrap): New procedure.
(%standard-phases): Add the wrap phase.
