treewide: enableParallelBuild -> enableParallelBuilding

pkgs/desktops/plasma-5/khotkeys.nix

···
     plasma-framework plasma-workspace qtx11extras
   ];
   outputs = [ "out" "dev" "bin" ];
-  enableParallelBuild = false;
+  enableParallelBuilding = false;
 }

pkgs/development/libraries/qt-5/5.9/qtlocation.nix

···
     moveToOutput "$qtQmlPrefix" "$bin"
   '';
   # Linking with -lclipper fails with parallel build enabled
-  enableParallelBuild = false;
+  enableParallelBuilding = false;
 }