[nostalgia,olympic] Fix pack tool build for Windows

src/nostalgia/modules/core/src/keel/keelmodule.cpp

@@ -92,7 +92,7 @@ static class: public keel::Module {
 				},
 			};
 		}
-} mod;
+} const mod;
 
 keel::Module const*keelModule() noexcept {
 	return &mod;

src/nostalgia/modules/core/src/studio/studiomodule.cpp

@@ -25,7 +25,7 @@ static class: public studio::Module {
 		out.emplace_back(ox::make<studio::ItemMakerT<core::Palette>>("Palette", "Palettes", FileExt_npal));
 		return out;
 	}
-} mod;
+} const mod;
 
 const studio::Module *studioModule() noexcept {
 	return &mod;