Print runtime warning in previews. (#135) #441

Job	Run time
Linux (debug)	51s
Library evolution	35s
Examples (Debug, 15.4)	6m 10s
Linux (release)	48s
macOS (debug, 15.2)	1m 10s
Examples (Debug, 16.0)	7m 27s
macOS (debug, 15.4)	1m 8s
Examples (Release, 15.4)	7m 13s
macOS (debug, 16.0)	1m 19s
SwiftWasm (wasm-5.9.2-RELEASE)	51s
Examples (Release, 16.0)	7m 31s
Windows (windows-latest, debug)	1m 44s
macOS (release, 15.2)	55s
SwiftWasm (wasm-5.10.0-RELEASE)	45s
Windows (windows-latest, release)	1m 46s
macOS (release, 15.4)	42s
macOS (release, 16.0)	1m 6s
	42m 1s

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