RFE: support using mmdebstrap (instead of debootstrap)

[andhe]

mmdebstrap is an alternative to using debootstrap. More info at https://packages.debian.org/unstable/mmdebstrap or https://gitlab.mister-muffin.de/josch/mmdebstrap

Note that mmdebstrap does NOT support --foreign (or --second-stage), however in a recent commit1 (not yet in any released version as currently 0.2.0 is the latest version of mmdebstrap) it is possible to leverage that proot supports using qemu to transparently emulate when the foreign architecture does not match the native one. Thus it could possibly work to use mmdebstrap in proot mode in debos, assuming it's possible to use proots qemu mode inside debos qemu usage.

(I'm not aware of any plans to implement --foreign (or --second-stage) in mmdebstrap.)

I think it would be nice if it could be possible to use mmdebstrap instead of debootstrap when building a recipe.

Open questions:

• should mmdebstrap usage be specified in the recipe or by the invoker of debos?
• mmdebstrap support more --variant=... than debootstrap does, should these be exposed?

A deal-breaker that needs to be investigated is also if proot qemu mode will at all work inside debos qemu. Hopefully this is a non-issue, but I can't tell.

[gl-yziquel]

The problem being that the proot package is broken.

I had to recompile a custom proot from latest releases. But it's not packaged in debian.