Daniel Gröber (dxld) authored Dec 11, 2018 and Ben Gamari committed Dec 12, 2018

Previously when switching from using a Plugin with
`RecompMaybe`/`ForceRecompile` in `pluginRecompile` to a Plugin with
`NoForceRecompile` GHC would never even consider recompiling.

However the previously active plugin could have modified the
compilation output so we should recompile.

Test Plan: validate

Reviewers: bgamari, mpickering

Subscribers: mpickering, rwbarton, carter

GHC Trac Issues: #15858

Differential Revision: https://phabricator.haskell.org/D5299