Do not parallelize definition building if it gives no advantage (#10776) #2913

Job	Run time
build_matrix	3m 47s
build (17, test-suite-http-server-tck-netty:nativeTest)	9m 34s
build (17, test-suite-http2-server-tck-netty:nativeTest)	11m 28s
build (17, test-suite-logback-graalvm:nativeTest)	8m 11s
build (17, test-suite-netty-ssl-graalvm:nativeTest)	9m 25s
build (21, test-suite-http-server-tck-netty:nativeTest)	9m 52s
build (21, test-suite-http2-server-tck-netty:nativeTest)	11m 22s
build (21, test-suite-logback-graalvm:nativeTest)	8m 20s
build (21, test-suite-netty-ssl-graalvm:nativeTest)	9m 33s
	1h 21m 32s

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