Bugfix/fix redundant compiler flags (#658)

* Improved GCC compiler flags in ARM, OS, and test builds. Removed redundant flags, and made them consistent across various builds.

* Fixed redundant redeclaration of various functions detected by change in compiler flags.

* Fixed string truncation warning in bip-init detected by change in compiler flags.

* Fixed some set-but-not-used variables by creating dummy functions instead of using macros.

ports/linux/bip-init.c

@@ -899,7 +899,7 @@ bool bip_init(char *ifname)
     int sock_fd = -1;
 
     if (ifname) {
-        strncpy(BIP_Interface_Name, ifname, sizeof(BIP_Interface_Name));
+        snprintf(BIP_Interface_Name, sizeof(BIP_Interface_Name), "%s", ifname);
         bip_set_interface(ifname);
     } else {
         bip_set_interface(ifname_default());