sdl3: fix building for static windows

pkgs/by-name/sd/sdl3/package.nix

@@ -173,7 +173,8 @@ stdenv.mkDerivation (finalAttrs: {
     # Many dependencies are not directly linked to, but dlopen()'d at runtime. Adding them to the RPATH
     # helps them be found
     NIX_LDFLAGS =
-      lib.optionalString (stdenv.hostPlatform.extensions.sharedLibrary == ".so")
+      lib.optionalString
+        (stdenv.hostPlatform.hasSharedLibraries && stdenv.hostPlatform.extensions.sharedLibrary == ".so")
         "-rpath ${
           lib.makeLibraryPath (finalAttrs.dlopenBuildInputs ++ finalAttrs.dlopenPropagatedBuildInputs)
         }";
@@ -230,7 +231,7 @@ stdenv.mkDerivation (finalAttrs: {
     changelog = "https://github.com/libsdl-org/SDL/releases/tag/${finalAttrs.src.tag}";
     license = lib.licenses.zlib;
     maintainers = with lib.maintainers; [ getchoo ];
-    platforms = lib.platforms.unix;
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
     pkgConfigModules = [ "sdl3" ];
   };
 })