* chore: add GN linter
* chore: fix GN lint errors
* try some crazy bash to get a gn exe
* base64 on linux is different
* cloning build_tools doesn't download GN
* download_from_google_storage needs depot_tools in the path
* fixup! chore: add GN linter
In the GN build, libchromiumcontent is no longer a distinct library, but
merely a container for a set of scripts and patches. Maintaining those
patches in a separate repository is tedious and error-prone, so merge
them into the main repo.
Once this is merged and GN is the default way to build Electron, the
libchromiumcontent repository can be archived.