Ensure programs compiled with DDC can compile and run with sound null safety

[nshahan]

To compile DDC needs a sound .dill file of the sdk libraries.

To run compiled code the build/test/run systems needs access to a sound version of the sdk libraries compiled to Javascript.

[sigmundch]

Will we need additional changes in frontend server to support this in flutter web?

[nshahan]

flutter/engine#19162 is in progress to build the sound js file but I think there will need to be more work to make sure the right version is being used when running with --sound-null-saftety.

[nshahan]

Tracking issue in the build repo: dart-lang/build#2723

[leafpetersen]

This is a blocker for the beta release, yes? Status on it?

[nshahan]

@jakemac53 Where do we stand at this point with the branch you were working on in the build repo?

[jakemac53]

I got blocked for a bit waiting for an sdk release and got side-tracked with some other things. I could pick it back up soon though.

[sigmundch]

@jakemac53 - just curious if you have any updates or if you need anything from us

[jakemac53]

I have started back on this, hit another blocker on our end which I have a PR out for and then I can resume.

[franklinyow]

Is this still a Beta issue? The issue that block this (#43097) is in post Beta. So we need to decide which is the correct timeframe.