Leave WebGPU/Vulkan CI serialized

Author: reeselevine

.github/workflows/build.yml

@@ -502,7 +502,7 @@ jobs:
         id: cmake_build
         run: |
           export Dawn_DIR=dawn/lib64/cmake/Dawn
-          cmake -B build -DGGML_WEBGPU=ON
+          cmake -B build -DGGML_WEBGPU=ON -DGGML_WEBGPU_SERIALIZE_SUBMIT=ON
           cmake --build build --config Release -j $(nproc)
 
       - name: Test