pinta: re-added missing runtime icons

On PR #155224, we switched to `dotnet build` to copy the Pinta assets to
the derivation. This worked mostly fine, however it seems to have missed
the runtime icons. We didn't catch the issue on #155224 neither,
probably because of some resource cache somewhere.

This commit re-adds the missing runtime icons by copying them manually.

pkgs/applications/graphics/pinta/default.nix

@@ -63,6 +63,10 @@ buildDotnetModule rec {
     # Rename the binary
     mv "$out/bin/Pinta" "$out/bin/pinta"
 
+    # Copy runtime icons
+    mkdir -p $out/share/icons/hicolor/16x16/
+    cp -r Pinta.Resources/icons/hicolor/16x16/* $out/share/icons/hicolor/16x16/
+
     # Install
     dotnet build installer/linux/install.proj \
       -target:Install \