cmake HAVE_POSIX_FORK examples

logicalclocks/rondb storage/ndb/rest-server2/extra/simdjson/simdjson-3.12.0/cmake/developer-options.cmake :232

check_symbol_exists(fork unistd.h HAVE_POSIX_FORK)

RavEngine/RavEngine deps/simdjson/cmake/developer-options.cmake :232

check_symbol_exists(fork unistd.h HAVE_POSIX_FORK)