build: add fib configuring option

Allow to select 8-8-8-8 or 16-8-8 mtrie FIB implementation.

Type: improvement

Change-Id: I2f4aec8bfec987d3f3d9f9cc5a16fabf4b6cc2ac
Signed-off-by: Benoît Ganne <bganne@cisco.com>

configure

@@ -33,6 +33,7 @@ OPTIONS:
   --wipe, -w              Wipe whole repo (except startup.* files)
   --sanitize, -s          Enable sanitizer (mem)
   --platform, -p          Specify target platform
+  --option, -o            Enable specific VPP options (fib8, fib16)
 __EOF__
 }
 
@@ -104,6 +105,19 @@ while (( "$#" )); do
 	  ;;
       esac
       ;;
+    -o|--option)
+      shift 1
+      case "$1" in
+	fib8)
+	  shift 1
+	  args+=("-DVPP_IP_FIB_MTRIE_16=OFF")
+	  ;;
+	fib16)
+	  shift 1
+	  args+=("-DVPP_IP_FIB_MTRIE_16=ON")
+	  ;;
+      esac
+      ;;
     -*|--*=) # unsupported flags
       echo "Error: Unsupported flag $1" >&2
       exit 1