mac build/builder improvements
Improve, refactor and clean up `tools/osx/builder` to build a relatively full-featured ffmpeg as well. This requires lots of other dists. It's kind of like a mini port system now. Will generalize it shortly to a sourced library for using with both the mac and the mingw builds. Will hopefully become a separate repo on github at some point. Add perl dist support to the builder. Add an `--env` flag to the builder to print the build environment variables so that they can be read in with `eval` for debugging purposes. Also add the `FFMPEG_STATIC` cmake option to link static ffmpeg libraries correctly. Move the codesigning and zipping of the `.app` bundle to the builder script and out of cmake, as this is something most users don't need.