Support dev on Windows.

We explicitly support dev tools (in `Makefile`) for Linux Ubuntu by running them with Ubuntu in our CI workflow. This combined with maintainers using Mac OS's to develop means that dev tools are well supported for Linux and Mac. But, dev tools are not well supported for Windows.

In `CI_win.yml` we run the matrix build on Windows and Linux, but we exclude Windows from some of the steps. Including Windows would better support dev tools for Windows.

This may mean making some adjustments to the dev tools themselves, e.g. determining the OS and conditionally setting filepath syntax at runtime.

Start by comparing the Windows exclusions in CI_win.yml with the development-tool commands defined in Makefile. Identify which excluded steps and tools fail on Windows, then verify that the relevant CI steps run successfully on Windows and that the development tools handle Windows path syntax correctly.

Written by the indexing model from the issue text.