Windows build does not support snapshots
After recently updating my MSys2/mingw-64 system I found that dt executables no longer supported snapshots in darkroom. I have checked that this is a build environment problem by reverting to an earlier system (from a backup) and snapshots work again. One major change in the update of the build environment was gcc going from 8.3 to 9.2, but then 9.2 is fine with Ubuntu. I don't know how to pin down the issue any further than this.