www/waterfox: unbreak fetch as HEAD commit moved

git archive maybe non-reproducible due to embedded decorative ref names:
https://github.com/MrAlex94/Waterfox/blob/eadf0f15d05e/addon-sdk/source/.gitattributes#L5
https://github.com/MrAlex94/Waterfox/blob/eadf0f15d05e/addon-sdk/source/python-lib/cuddlefish/_version.py#L12

Reported by: jrm