* pkg(pony-0.39.0): Add pony-lang 0.39.0
* pkg(pony-0.39.0): Use `git submodule` to install llvm and get the source through cloning.
* pkg(pony-0.39.0): Reset to 0.39.0 commit and cd into `ponyc`
* pkg(pony-0.39.0): User proper installation instructions, like specified in the installation guide
* pkg(pony-0.39.0): Setup compile script.
* pkg(pony-0.39.0): Properly delete the build dir.
* pkg(pony-0.39.0): Get rid of author key in metdata
* pkg(pony-0.39.0): `CD` into `ponyc` right before cloning.
* pkg(ponyc-0.39.0): Move `cd` to the correct palce.
Shivansh-007