clapper: fix opening files (#414535)

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

···
 
     mkdir -p $out
     lndir $src $out
+    dbusfile=share/dbus-1/services/com.github.rafostar.Clapper.service
+    rm $out/$dbusfile
+    cp $src/$dbusfile $out/$dbusfile
+    substituteInPlace $out/$dbusfile \
+      --replace-fail $src/bin/clapper $out/bin/clapper
 
     runHook postInstall
   '';