ci: only compare generation on Linux (faster)

Signed-off-by: Henry Schreiner <[email protected]>

Author: henryiii

.github/workflows/reusable-cookie.yml

@@ -91,9 +91,11 @@ jobs:
         run: nox -s 'tests(mesonpy, novcs, sphinx)'
 
       - name: Compare copier template generation
+        if: runner.os == "Linux"  # No need to check this on each (slow on Windows)
         run: nox -s compare_copier
 
       - name: Compare cruft template generation
+        if: runner.os == "Linux"  # No need to check this on each (slow on Windows)
         run: nox -s compare_cruft
 
   nox: