Evaluate all child processes in the temporary directory, and use
`std.fs.path.relative` to make every other path relative to that child
cwd instead of our cwd.
Resolves: #22119
Instead of introducing YES_COLOR, a completely new standard, into the mix
it might make more sense to instead tag along with the CLICOLOR_FORCE env var,
which dates back to at least 2000 with FreeBSD 4.1.1 and which is
supported by tools like CMake.
<https://bixense.com/clicolors/>