clerk: fix reference to wrapped binary in wrapper

Due to the use of pushd/cd the reference to the wrapper binary was a
relative path.  This does not work in general as it is depending on the
working directory where the wrapper is executed.

pkgs/by-name/cl/clerk/package.nix

@@ -74,13 +74,11 @@ stdenv.mkDerivation {
       ];
     in
     ''
-      pushd $out/bin
       for f in clerk clerk_rating_client; do
-        wrapProgram $f \
+        wrapProgram $out/bin/$f \
           --prefix PATH : "${binPath}" \
           --set PERL5LIB $PERL5LIB
       done
-      popd
     '';
 
   passthru.updateScript = unstableGitUpdater {