Nimble file broken on Windows and Nim 1.6

[Vindaar]

Just leaving these here quickly so I don't forget.

With the latest changes, the Nimble file is problematic both on Windows targets as well as for Nim 1.6 (on any target).

See in the failing CI for Windows and Nim 1.6 here:
https://github.com/SciNim/Datamancer/actions/runs/11314998852/job/31465646405?pr=73

[lilkeet]

this is fixed on my fork, working on better backwards compat, then will do a pr.