Run windows_arm build only on main branch.

[godofredoc]

Dart SDK does not exist in beta or stable branches. This PR will limit the execution of this build to main branch only.

Bug: flutter/flutter#123288

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[loic-sharma]

@godofredoc Could you expand on why this is necessary? Is Dart's support for Windows ARM disabled on stable and beta? Does that mean that Flutter stable and beta won't be able to support Windows ARM? /cc @pbo-linaro

[godofredoc]

@godofredoc Could you expand on why this is necessary? Is Dart's support for Windows ARM disabled on stable and beta? Does that mean that Flutter stable and beta won't be able to support Windows ARM? /cc @pbo-linaro

That is correct, this is the initial bug: flutter/flutter#113931

The TLDR; is that Dart SDK support for windows arm is considered experimental and not currently shipped to beta or stable channels.

[pbo-linaro]

And do you think it could be possible to collaborate with Dart team to enable this, with Flutter dev team support?

[godofredoc]

cc'ing @timsneath who can provide more info about the dart sdk windows arm strategy.

[timsneath]

We are super-excited for the (Flutter, Windows, ARM) tuple to be checked! (I'm particularly excited -- I have more ARM than Intel machines running Windows...)

As I understand it, the lay of the land is that we're still standing up our test CI infrastructure to fully support ARM: we have an array of Volterra devices that will be up and running in the next couple of months. When we have that enabled, we'll have the infrastructure to be able to consistently run test suites on Windows/ARM, which is a prerequisite to us being able to declare beta or stable. And yes -- it's of course our goal that Flutter supports Windows/ARM, thanks in large part to your contributions.

While we get the test labs spun up, we'd be delighted to see you continue to work on proving this out on the master channel, so that we're ready as soon as possible. Excited to make some noise about this!

[pbo-linaro]

Good to hear you're on track to support Windows on Arm with dedicated machines 👍.
For now, at Flutter level, we can enable it for master channel only, and later, to beta and stable.