CMake: Bump maximum policy version to 4.2 #908

Job	Run time
POSIX (ubuntu-latest, cmake)	2m 21s
POSIX (macos-latest, autotools)	5m 54s
POSIX (macos-latest, cmake)	5m 49s
POSIX (ubuntu-latest, autotools)	5m 53s
POSIX (ubuntu-24.04-arm, autotools)	6m 6s
POSIX (ubuntu-24.04-arm, cmake)	2m 30s
	28m 33s

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