Qt5.15 and mac-13 #123

Job	Run time
build (ubuntu-latest, linux, 6.5)	1m 50s
build (macos-13, mac, 5.15, qtmacextras)	1m 6s
build (ubuntu-latest, linux, 5.15, qtx11extras icu)	7m 15s
	10m 11s

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