Fix embedder glfw examples cmake subdirectory path error

[hongeSunCoder]

Fix just a cmake glfw subdirectory path error in embedder examples.

Fix: flutter/flutter#138340

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• All existing and new tests are passing.

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie or stuartmorgan on the #hackers channel in Chat (don't just cc them here, they won't see it! Use Discord!).

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

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[bdero]

LGTM!

[auto-submit]

auto label is removed for flutter/engine/48013, due to This PR has not met approval requirements for merging. You are not a member of flutter-hackers and need 1 more review(s) in order to merge this PR.

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[zanderso]

lgtm, but as the message says, this PR will need a test exemption requested in the Discord room.

[bdero]

Whoops, slipped my mind. Asked for one in Discord.

[Hixie]

test-exempt: build script