Fix Vulkan embedder example

[nanokatze]

Fix a just outright syntax error in CMakeLists of vulkan_glfw and specify a missing include for std::chrono stuff.

Fixes: flutter/flutter#118957

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[chinmaygarde]

This seems like a fine fix. Can you address the CLA so we can make progress?

Also, per @zanderso, we should figure out how to run these examples on CI. But it may require us to get CMake and related tools on the bots.

[nanokatze]

This seems like a fine fix. Can you address the CLA so we can make progress?

I have? cla/google has green checkmark for me.

[chinmaygarde]

Hmm, not sure why the bot didn't update. Check check mark in the presubs is green though. All good.