Disable explicit optimisation

Cabal still complains.

(Cabal is still going to compile with -O, tho. Or so it says.)

guide.cabal

@@ -62,7 +62,7 @@ executable guide
                      , wai-middleware-metrics
                      , wai-middleware-static
                      , xss-sanitize
-  ghc-options:         -Wall -O -fno-warn-unused-do-bind
+  ghc-options:         -Wall -fno-warn-unused-do-bind
                        -threaded -with-rtsopts=-T
   hs-source-dirs:      src
   default-language:    Haskell2010