* build: [gn] explicitly override rtc_use_h264
* build: [gn] don't override ffmpeg config from release config
* build: [gn] remove is_cfi override from release config
The original concern about node is fixed and we have been
building testing builds without the override for sometime now.
* build: [gn] add distributable zip target
* build: update the CircleCI config
- enable debug and testing builds on Mac
- run Mac release builds nightly
- run test for Mac release builds
- use shared build machines configs
* Add resources dir to zip on non mac platforms.
Devs can still locally override or add settings by adding lines after
the `import` statement in args.gn.
This will help make sure that everyone has a common set of build args,
and will allow us to update everyone's build args in git.
