Skip noarch build if --noarch-platform == build_platform

[hadim]

See #1175 for context.

When --noarch-platform is set, the noarch builds will be skipped if they are being built on a different platform than the platform set.

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It's an opinionated flag, and the idea is to make it easy to build single repos rattler-based forge. By setting this flag to linux-64 for example, all the noarch packages of the forge will be only built on the linux-64 CI runs and not the others.

If that too specific for rattler-build, let me know and I will close.

[wolfv]

I did a tiny bit of cleanup to remove the unwrap :)

I am wondering if we shoudl call this --noarch-build-platform=..., and similar in the code. I think that would make it very clear? What do you think @hadim?

[hadim]

I did a tiny bit of cleanup to remove the unwrap :)

Thanks!

I am wondering if we shoudl call this --noarch-build-platform=..., and similar in the code. I think that would make it very clear? What do you think @hadim?

I switched to --noarch-build-platform.

LGTM.