Add a FORK_UNION_BUILD_TESTS option to the cmake #52

Job	Run time
Cross-compilation (i386)	2m 10s
Ubuntu (GCC)	2m 5s
Update Version	6s
Ubuntu (Clang)	3m 27s
Windows MSVC Versions (v143, RelWithDebInfo)	2m 53s
Windows MSVC Versions (v143, Debug)	3m 21s
Windows MSVC Versions (v143, Release)	2m 59s
macOS	1m 43s
Windows MSVC Versions (v142, RelWithDebInfo)	2m 49s
Windows MSVC Versions (v142, Debug)	2m 55s
Windows MSVC Versions (v142, MinSizeRel)	2m 52s
Windows MSVC Versions (v143, MinSizeRel)	3m 21s
Windows MSVC Versions (v142, Release)	3m 1s
Cross-compilation (armhf)	2m 27s
Windows	3m 23s
macOS LLVM Versions (16, MinSizeRel)	1m 45s
macOS LLVM Versions (16, Release)	1m 10s
macOS LLVM Versions (17, Release)	1m 0s
macOS LLVM Versions (16, RelWithDebInfo)	1m 34s
macOS LLVM Versions (17, Debug)	1m 54s
macOS LLVM Versions (16, Debug)	1m 42s
macOS LLVM Versions (18, Release)	1m 25s
macOS LLVM Versions (18, Debug)	1m 34s
macOS LLVM Versions (18, MinSizeRel)	1m 17s
macOS LLVM Versions (19, Release)	1m 29s
macOS LLVM Versions (17, MinSizeRel)	1m 34s
macOS LLVM Versions (19, Debug)	1m 39s
macOS LLVM Versions (19, MinSizeRel)	2m 36s
macOS LLVM Versions (18, RelWithDebInfo)	2m 1s
macOS LLVM Versions (20, Debug)	1m 46s
macOS LLVM Versions (20, Release)	1m 0s
macOS LLVM Versions (19, RelWithDebInfo)	1m 22s
macOS LLVM Versions (20, MinSizeRel)	1m 42s
macOS LLVM Versions (17, RelWithDebInfo)	1m 47s
macOS LLVM Versions (20, RelWithDebInfo)	1m 18s
Cross-compilation (s390x)	8m 30s
	1h 19m 37s

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