CMake

Remove GitHub actions that do not work anymore and simplyfy our CMake… #76

Job	Run time
build (ubuntu-latest, Debug, static, 5.12)	1m 12s
build (ubuntu-latest, Debug, static, 6.6.0)	2m 10s
build (ubuntu-latest, Debug, shared, 5.12)	46s
build (ubuntu-latest, Debug, shared, 6.6.0)	1m 33s
build (ubuntu-latest, Release, static, 5.12)	1m 16s
build (ubuntu-latest, Release, static, 6.6.0)	1m 6s
build (ubuntu-latest, Release, shared, 5.12)	41s
build (ubuntu-latest, Release, shared, 6.6.0)	1m 25s
build (windows-latest, Debug, static, 5.12)	2m 13s
build (windows-latest, Debug, static, 6.6.0)	2m 59s
build (windows-latest, Debug, shared, 5.12)	1m 43s
build (windows-latest, Debug, shared, 6.6.0)	2m 8s
build (windows-latest, Release, static, 5.12)	1m 21s
build (windows-latest, Release, static, 6.6.0)	2m 54s
build (windows-latest, Release, shared, 5.12)	2m 9s
build (windows-latest, Release, shared, 6.6.0)	2m 2s
build (macos-latest, Debug, static, 5.12)	56s
build (macos-latest, Debug, static, 6.6.0)	1h 14m 47s
build (macos-latest, Debug, shared, 5.12)	1m 46s
build (macos-latest, Debug, shared, 6.6.0)	1m 41s
build (macos-latest, Release, static, 5.12)	1m 9s
build (macos-latest, Release, static, 6.6.0)	2m 1s
build (macos-latest, Release, shared, 5.12)	1m 18s
build (macos-latest, Release, shared, 6.6.0)	2m 55s
	1h 54m 11s

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