use boost to get exec path or fallback to usr/local/bin
use boost to get exec path or fallback to usr/local/bin

give 5 options to find geth and relayer, use boost lib to get executable path in one of the options


Former-commit-id: 5b48710c23c379574d7551bbf412e3943ee37b48
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin