Build

Use Qt 6 for macOS workflow #768

Job	Run time
macOS (3.13, 6.11.*, debug)	34s
ubuntu (22.04)	34s
ubuntu (24.04)	34s
windows (win64_msvc2019_64, 3.13, x64, 5.15.*, PythonQtCore PythonQtGui PythonQtMultimedia)	34s
oldschool (rockylinux, 9, debug)	33s
oldschool (rockylinux, 9, release)	32s
windows (win32_mingw53, 3.6, x86, 5.11.*)	37s
macOS (3.13, 6.11.*, release)	34s
windows (win64_mingw73, 3.10, 5.12.*, x64)	35s
windows (win64_msvc2017_64, 3.6, x64, 5.11.*)	34s
	5m 41s

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