cmake LIBCXX_HAS_RT_LIB examples

Lewuathe/mlir-hello thirdparty/llvm-project/libcxx/cmake/config-ix.cmake :131 

check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)

PlatONnetwork/pWASM libc++/libcxx/cmake/config-ix.cmake :86 

check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)

CTSRD-CHERI/cheribsd contrib/subrepo-cheri-libc++/cmake/config-ix.cmake :130 

check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)