Fix failing tests

- Add required .yaml files as "extra-source-files" to the
  cardano-launcher cabal project. This allows Nix to find the data
  files required for the tests (when paired with keepSource = true).

cardano-launcher/cardano-launcher.cabal

@@ -11,6 +11,9 @@ copyright:      2018 IOHK
 license:        Apache-2.0
 license-files:  LICENSE, NOTICE
 build-type:     Simple
+extra-source-files:
+    configuration/launcher/jormungandr/launcher-config-qa.linux.yaml
+    configuration/launcher/jormungandr/launcher-config-qa.windows.yaml
 
 source-repository head
   type: git

nix/haskell.nix

@@ -49,8 +49,6 @@ let
         # These tests need files from the source tree.
         packages.cardano-launcher.components.tests.cardano-launcher-test.keepSource = true;
 
-        packages.cardano-launcher.components.tests.cardano-launcher-test.preCheck = "cd $src/cardano-launcher";
-
         # Packages we wish to ignore version bounds of.
         # This is similar to jailbreakCabal, however it
         # does not require any messing with cabal files.