make drachtio more hardened

[asarubbo]

Hello Dave,

while recent version of gcc compile by default with many hardening flags ( but it may depends on the distro choice) I think it is worth add a bit of hardening here.

You can take hints from here: https://wiki.gentoo.org/wiki/Hardened/Toolchain#Changes

The checksec program also helps to understand how it was compiled.

# checksec --file /usr/local/bin/drachtio 
RELRO           STACK CANARY      NX            PIE             RPATH      RUNPATH      Symbols         FORTIFY Fortified       Fortifiable  FILE
Partial RELRO   No canary found   NX enabled    PIE enabled     No RPATH   No RUNPATH   17750 Symbols   No      0               48      /usr/local/bin/drachtio

I compiled it with hardening flags and there were no issue so far on my side