Path: Add missing else clause on version statement
Path: Add missing else clause on version statement

This was wrong on many level:
- The missing `else` clause meant that the `enforce` clause was always there on Windows;
- The `enforce("Reason")` should have been `enforce(false, "Reason")`,
  as in its current form it would never fail and not serve its intended purpose;
- It was pushing at runtime something that was easily detected at CT;

Geod24/dub