Add small bubblewrap like program as a build step

[MaxHearnden]

This allow the user to perform a rootless build without bubblewrap on machines with user namespaces enabled

[fosslinux]

I understand the idea/implementation in principle. Would you mind outlining any particular, specific usecases for this?

[MaxHearnden]

It's to reduce the binary seed required for an unprivileged build to just hex0+kaem-optional and can be used with the following commands

cp sysa/stage0-posix/src/* .
cp sysa/after_wrap.kaem after.kaem

# This stage could be integrated into after_wrap.kaem
echo "CHROOT=True
CHROOT_WRAP=True" >> sysa/bootstrap.cfg

./bootstrap-seeds/POSIX/x86/kaem-optional-seed

[oriansj]

I like it but 2 minor details:

1. the syscalls should added to M2libc such that the code becomes more standard C.
2. the wrap.c program belongs in mescc-tools-extra which live-bootstrap does already use and will allow other bootstrapping projects to leverage your work.

great work

[fosslinux]

If this could be

1. rebased on master
2. updated to reflect that wrap.c is in mescc-tools-extra

I think I'm happy to include this in principle.

[Googulator]

#436 will bring in wrap.c into live-bootstrap, although currently unused

[MaxHearnden]

Replaced by #479