[guyfleeman]

Caught some funnies switching between Nix and native working on distribution builds.

• Move some generated files to the build folder which is the correct solution to some cache invalidation problems. It also adds a function that detects when compilers changes, indicating you've switched environments. If forces you to clean on those.
• Add a flag to gate march-native (current behavior preserved by default).
• Add a Ubuntu native (non nix) CI target that'll be the future landing point of deb/self contained distributions.
• adds firewire lib to dependencies (this one slipped thru).