all targets should at least build

we'll also run the tests after which is great, but this at least gets us some
automatic checking of our executables which aren't really covered by automated
tests

flake.nix

@@ -58,7 +58,7 @@
 
             text = ''
               cabal update hackage.haskell.org
-              cabal build
+              cabal build all
               cabal run tests
             '';
           }