Enable specifying a platform for build

[richlander]

We should enable people to build x64 images on Arm64 machines. The cloud is still mostly x64.

Updating tags to switch between x64 and Arm64 isn't great. It's inconvenient and alters assets under source control. Also, .NET has architectural-specific aspects (RIDs), however, we've been able to make that work well with --platform.

Here is where we are headed with .NET: dotnet/dotnet-docker#4388

[bwateratmsft]

We talked about this some in standup yesterday. Command customization already facilitates this for non-task scenarios, and adding support for a flag to control --platform to the docker-build task is pretty straightforward.

[richlander]

Can you folks write a tutorial for this?

[spboyer]

@bwateratmsft tried adding
"platform" : "linux/arm64" to dockerBuild section and it is not picked up in the command when run, where is the proper place to insert?

[bwateratmsft]

@spboyer It's not supported by the extension code yet, what I meant was it wouldn't be difficult to add support.

[spboyer]

I suggest adding the "platform" option in the "docker-build: debug" and "docker-build: publish" tasks when scaffolding occurs with the local architecture defaulted there.

We can add a tutorial for creating additional and/or editing.

[bwateratmsft]

I think we should only add it for the release build task. Adding it to the debug build task would result in a debug config that may not work across different platforms. (i.e., same repo, different machines).

[spboyer]

Good point.

[richlander]

I think you mean publish but that makes sense.

[stormwind85]

Hello !
Can't wait about the next release.

What about this issue ?
Could you validate the associated MR ? ~> #3874