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: d33184bd4b47533c6ce728ad8c88be92d58cc7a9
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin