解决new open source的cmake issue

在cmake的时候报错

1.在cmakelists里面加上cmake_policy(SET CMP0026 OLD)

/home/lora/gr-lora_sdr/lib/frame_sync_impl.cc:406:49: error: call of overloaded ‘abs(uint32_t)’ is ambiguous
                         if (abs(bin_idx-net_id_2)>1){ //wrong network identifier

解决方法：

gedit /home/lora/gr-lora_sdr/lib/frame_sync_impl.cc

然后把文件中的abs替换成fabs或者labs，cd到源文件夹，删除build，重新安装。