cmake HAS_W examples

gatecat/nextpnr-xilinx CMakeLists.txt :139 

check_cxx_compiler_flag("-W${TRY_WARN_FLAG}" HAS_W${TRY_WARN_FLAG})

YosysHQ/nextpnr CMakeLists.txt :156 

check_cxx_compiler_flag("-W${TRY_WARN_FLAG}" HAS_W${TRY_WARN_FLAG})