Replace dev-opt profile by only building dependencies using full optimizations.
Doing a bit more research this might actually be the preferable approach as building dependencies happens only once (when the VM image is prepared) and yields smaller dependencies speeding up the link times of the final harvester binary (and improving its runtime when it spends time in the dependencies e.g. parsing HTML).
Doing a bit of unscientific testing by making a trivial modification of a single harvester, this does indeed reduce incremental rebuild time from 60s to 10s.