Expose runner cfg as optional third argument

[feeltheburns]

When dealing with cross compilation environments, there are cases where it is beneficial to have the runner cfg be "exec" instead of "target".

[keith]

can you share an example of where this needs the exec config?

[feeltheburns]

can you share an example of where this needs the exec config?

Here is the use case:

I have a deploy target that is a multirun, that is called like this (note the arm config points to a arm toolchain:
bazel run --config=arm //:deploy_to_pi

That looks something like this

multrirun(
   name = "deploy_to_pi",
   commands = [
     :deploy_script,
     :verify_deployed_script,
   ]
)

Where deploy_script and verify_deployed_script are sh_binary() targets and at depend on an executable for the pi, which requires the arm cross compilation toolchain. While the shell scripts need to be run on the host "exec" context.

When running without my patch, I get the follow error type as it's trying to use the python interpreter for arm when processing the multirun command.

OSError: [Errno 8] Exec format error

[alextac98]

This would be a useful feature when you use bazel as a build orchestrator and a run orchestrator, which it should be able to handle. Excited to see this in main if it works with the vision of the maintainer, I currently apply this patch to the module for my projects

[keith]

can you fix the ci job, and add a quick test for this that transitions the multirun to some weirdo platform and proves that it still works?