Enable GitHub actions CI for stable/13 as well

[arichardson]

Summary

All cross-building patches have been merged to stable/13 so it should
also build fine on macOS+Linux.

I'm not sure if committing this change will break the github mirror.

[arichardson]

@uqs Should I commit this to stable/13 and we see if the github mirror still works or would you prefer to do it?

[uqs]

In D29831#669973, @arichardson wrote:

@uqs Should I commit this to stable/13 and we see if the github mirror still works or would you prefer to do it?

Ah, you mean because of the workflow push? I think it is fine to change the existing file, only the initial creation somehow needs to be special cased.

[arichardson]

In D29831#669974, @uqs wrote:

In D29831#669973, @arichardson wrote:

@uqs Should I commit this to stable/13 and we see if the github mirror still works or would you prefer to do it?

Ah, you mean because of the workflow push? I think it is fine to change the existing file, only the initial creation somehow needs to be special cased.

Seems like it worked fine. I guess it was the initial creation only.