perfrevlogwrite: fix a typo in the option name The submitted patches was apparently damaged, and a 's' was missing.

fuzz: improve makefile per feedback from some folks at work This is a *ton* better. Once this lands, I can remove a nasty kludge from the oss-fuzz build.sh. Bonus: this fixes the coverage build. Differential Revision: https://phab.mercurial-scm.org/D5458