cmake LIBCXX_HAS_M_LIB examples

PlatONnetwork/pWASM libc++/libcxx/cmake/config-ix.cmake :85 

check_library_exists(m ccos "" LIBCXX_HAS_M_LIB)

CTSRD-CHERI/cheribsd contrib/subrepo-cheri-libc++/cmake/config-ix.cmake :129 

check_library_exists(m ccos "" LIBCXX_HAS_M_LIB)