ci: make macos_ci.yml more robust (use -no-parallel for the UI examples)

.github/workflows/macos_ci.yml

@@ -79,8 +79,8 @@ jobs:
           cd ui
           mkdir -p ~/.vmodules
           ln -s $(pwd) ~/.vmodules/ui
-          ../v examples/rectangles.v
-          ../v examples/users.v
+          ../v -no-parallel examples/rectangles.v
+          ../v -no-parallel examples/users.v
           ## ../v run examples/build_examples.vsh
       - name: V self compilation with -usecache
         run: |