The `set` command in `cmd` has terrible properties in that there's no
real structure to it. Sensitive sequences in values or variable names
that are escaping sequences can be interpreted at the wrong time or
things like newlines in values are not escaped at all and cause
ambiguities in parsing. Avoid all of that and use PowerShell to use JSON
as a communication mechanism.
The toolsets available on machines hosting shell runners will evolve
over time. Require the runners to have tags indicating that they have
specific toolsets available. When toolsets are eventually removed from
a runner, its tags can then be updated accordingly to prevent pipelines
created for old commits from ever running on them.
