Provide a flake "bundler" recovering the approach described in https://hpc.guix.info/blog/2020/05/faster-relocatable-packs-with-fakechroot/:

• fakechroot for filesystem access: https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/packages/aux-files/run-in-namespace.c,
• rtld audit for dynamic loading: https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/packages/aux-files/pack-audit.c.