This huge commit is a manual conversion, notes on what was
o project.conf defines the arch specific stuff which was
previously hardcoded into YBD, so the stage1 target and target
etc are all defined by the build-essential project.conf
o Direct and easy changes for git source representation
o Added stage1.bst & stage2.bst "stacks", everything built in
stage2 build-depends on stage1.bst, and the final build-essential
products build-depend on stage2.bst (note build-depend means
to depend _only_ for building, not propagated forward).
o Instead of using host tools we build on the GNOME flatpak
o Some build-essential morph files use $(dirname $(pwd)) for a sysroot,
which is weird, it means the morph files rely on building at one directory
below the slash sysroot - in buildstream we build in /buildstream/build
which is two - had to replace these with $(dirname $(dirname $(pwd))) instead
o Remove the devices sections from the fhs-dirs elements, not allowed
to create static device nodes in buildstream.