Commits on Jun 3, 2021

1. config: Move setUseOptipng call after we determine if optipng is avai… …

   …lable
   
   Currently we tell AsCompose to use optipng just based on the value of
   the feature flag. AsCompose will respect what we tell it without further
   checking. If optipng is in fact not available then we'll crash later on
   when we first try to use it.
   
   Fix this by setting the flag *after* we check if optipng is installed.

   Iain Lane committed Jun 3, 2021
   d8f0cdf