fe_archive.c was compiled only for the frontend in src/common/, but as
it will never share anything with the backend, it makes most sense to
move this file to src/fe_utils/.

Reported-by: Peter Eisentraut
Discussion: https://postgr.es/m/e9766d71-8655-ac86-bdf6-77e0e7169977@2ndquadrant.com
Backpatch-through: 13