cmake LIBBSD_HAS_GETPASS examples

CTSRD-CHERI/cheribsd contrib/libpcap/CMakeLists.txt :916 

check_library_exists(bsd getpass "" LIBBSD_HAS_GETPASS)

CTSRD-CHERI/cheribsd contrib/libpcap/CMakeLists.txt :919 

endif(LIBBSD_HAS_GETPASS)