Support mixed-arch HPC where leader and jobs need different Python interpreters

[unito-bot]

Bruno P Kinoshita from CWL4HPC has an HPC setup in Barcelona with x86_64 head nodes and ARM worker nodes. Toil supports ARM but only thinks about having single-architecture clusters, and the HPC virtualenv setup we use doesn’t really think about having to run the workers under a different Python interpreter.

We should try and support this cluster setup, and let you run the Toil leader on the head node and the Toil workers on ARM.

The workaround it so make sure the cluster lets worker nodes submit new jobs, and then run the leader as a job on the ARM workers.

┆Issue is synchronized with this Jira Story
┆Issue Number: TOIL-1687