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Fix build-demos-concurrently / get-demos failing #234

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Run time

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Job	Run time
build (4.2.5, html5)	19m 21s
build (4.2.5, hl)	20m 2s
build (4.2.5, flash)	15m 29s
build (4.2.5, cpp)	19m 59s
build (4.3.4, html5)	16m 26s
build (4.3.4, hl)	25m 42s
build (4.3.4, flash)	14m 13s
build (4.3.4, cpp)	21m 21s
	2h 32m 33s