Fix CMake build when building examples

Add subdirectory src/utils only once.

Change-Id: I3437e0a4c9ff250f4518ce485763117291889cd7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/31103
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Commit-Queue: dan sinclair <dsinclair@chromium.org>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d1cb467..4de37d4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -152,6 +152,7 @@
 add_subdirectory(src/utils)
 
 if (DAWN_BUILD_EXAMPLES)
-    add_subdirectory(src/utils)
+    #TODO(dawn:269): Add this once implementation-based swapchains are removed.
+    #add_subdirectory(src/utils)
     add_subdirectory(examples)
 endif()