release/vm: partially support NO_ROOT

[brooks]

Summary

For images that don't require QEMU, support NO_ROOT. This entails:

• Passing NO_ROOT down to mk-vmimage.sh (which sets it for installworld, etc)
• Handling etcupdate bootstrapping
• Adding assorted config file METALOG entries
• Running makefs in the right directory and adding -D for dups

The main gap in NO_ROOT support is package installation.

[jrtc27]

release/tools/vmimage.subr

71–78

${NO_ROOT:+-N} and drop the var?

211–212

Why the cd if you also use DESTDIR in sourcepath? (I can guess why the cd, but then should sourcepath not just be .[/METALOG]?)

[brooks]

Implement suggetions from @jrtc27

• Use shell variable substitutions instead of temporaries
• Use DESTDIR-relative paths in makefs calls

[emaste]

Looks reasonable. Perhaps also add comments on cases that still need NO_ROOT support?

release/tools/vmimage.subr

72

Add a comment here?

[brooks]

• Add a comment about the etcupdate metalog bits
• Require that both or neither of WITHOUT_QEMU and NO_ROOT be set

[brooks]

• fix BASIC-CI images (missing files)
• add some more abstraction to reduce the overall diff