Add warning for parallel builds #219

Job	Run time
get_version	6s
build-and-run-tests-windows	1h 0m 14s
build-and-run-tests-macos (macos-15-intel)	1h 11m 29s
build-and-run-tests-ubuntu	35m 38s
build-and-run-tests-macos (macos-14)	37m 48s
build-and-run-tests-windows	1h 1m 0s
build-and-run-tests-macos (macos-15-intel)	58m 13s
get_version	6s
build-and-run-tests-ubuntu	35m 38s
build-and-run-tests-macos (macos-14)	37m 48s
	6h 38m 0s

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