nwg-panel: move icon to spec-compliant location

Author: pancaek

pkgs/by-name/nw/nwg-panel/package.nix

@@ -66,9 +66,8 @@ python3Packages.buildPythonApplication (finalAttrs: {
     ++ [ libdbusmenu-gtk3 ];
 
   postInstall = ''
-    mkdir -p $out/share/{applications,pixmaps}
-    cp $src/nwg-panel-config.desktop nwg-processes.desktop $out/share/applications/
-    cp $src/nwg-shell.svg $src/nwg-panel.svg nwg-processes.svg $out/share/pixmaps/
+    install -D $src/nwg-panel-config.desktop nwg-processes.desktop -t $out/share/applications/
+    install -D $src/nwg-shell.svg $src/nwg-panel.svg nwg-processes.svg -t $out/share/icons/hicolor/scalable/apps/
   '';
 
   preFixup = ''