New package: gn-0.1915

[whoizit]

General

• This is a new package and it conforms to the quality requirements

Have the results of the proposed changes been tested?

• I use the packages affected by the proposed changes on a regular basis and confirm this PR works for me
• I generally don't use the affected packages but briefly tested this PR

Required for Dart pkg building and other projects (chromium, electron)
https://repology.org/project/gn/versions

I'm not exactly sure about the choice of license, because it uses the word owner, that not used in BSD-3-Clause

[q66]

no point in packaging this, gn is not stable so different things require different versions

[ericonr]

The GN readme recommends vendoring/using a git submodule for GN, so every project using it can track the necessary version by themselves. A system version wouldn't be very useful, and testing for updates would be painful.

[ericonr]

If you need a GN to build dart, it could be called dart-gn or similar, but I don't think being a template has helped in simplifying the build or something of the sort, so just bootstrapping it inside the dart build makes more sense to me.