Guard quickcheck.1 regeneration

Without this guard it will be regenerate on each run,
and cabal new-build considers whole package dirty.

ShellCheck.cabal

@@ -32,6 +32,7 @@ Extra-Source-Files:
 custom-setup
   setup-depends:
     base          >= 4     && <5,
+    directory     >= 1.2   && <1.4,
     process       >= 1.0   && <1.7,
     cabal-doctest >= 1.0.6 && <1.1,
     Cabal         >= 1.10  && <2.5