CMake: Add Haiku (BeOS-like) support #1900

Job	Run time
check (libclamav, (iana_cctld\|bytecode_api_\|bytecode_hooks\|rijndael\|yara\|inffixed\|inflate\|queue\|n...	23s
check (libfreshclam)	29s
check (clamav-milter)	29s
check (clambc)	23s
check (clamconf)	32s
check (clamd)	23s
check (clamdscan)	25s
check (clamdtop)	23s
check (clamonacc, (c-thread-pool\|fts\|priv_fts))	29s
check (clamscan)	25s
check (clamsubmit)	23s
check (freshclam)	23s
check (libfreshclam)	27s
check (common)	25s
check (sigtool)	25s
check (examples)	22s
check (win32/compat)	23s
	7m 9s

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