Support installing "bleeding edge" SDKs

[mit-mit]

Support installing "bleeding edge" builds from http://gsdview.appspot.com/dart-archive/channels/be/raw/latest/sdk/

One question is what is a good name for these?

1. Bleeding edge (don't love the word "bleeding")
2. Latest (potentially confusing with "latest" from a channel)
3. Nightlies (although these are not nightly builds)

[athomas]

I would prefer if we treat channels as branch names rather than a different namespace. For dev, beta and stable that is already true. We used be because it sorts alphabetically before dev but that is no longer important with the new versioning scheme. So can use main (anticipating the future name of the Dart SDK default branch). Then we can remove the be/Bleeding edge/edge terminology from various CI/release tooling later.

FYI, not sure if these builds will work on macOS (be builds aren't signed).

[mit-mit]

not sure if these builds will work on macOS (be builds aren't signed).

I seem to be able to run them if I right-click on the dart binary, select open, and then OK to the signing warning. After this dart runs without warning.

[athomas]

not sure if these builds will work on macOS (be builds aren't signed).

I seem to be able to run them if I right-click on the dart binary, select open, and then OK to the signing warning. After this dart runs without warning.

Yes, but anything that requires user interaction doesn't sound like an option on GitHub Actions. It's something we should just try.

[mit-mit]

Ah, yes of course, had not thought of that.

[mit-mit]

@athomas about macOS and signing, I wonder if perhaps we should consider doing a single daily edge build that has signing? Would that be possible?

[athomas]

I'm afraid we will have to re-do parts of our signing infra to do more signed builds. We may be hitting hard limits and be unable to sign other releases if we use what we have excessively.

[kevmoo]

google/mono_repo.dart#299

FYI – so we cannot migrate mono repo here (yet) because of this!

CC @jakemac53

[mit-mit]

Attempted fix in #16