scripts: ext-toolchain: actually probe libc type on config generation

Currently we never call probe_cc before config generation, this cause
the script to never actually detect the correct libc type.
Call probe_cc before config generation to correctl set the .config file.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

scripts/ext-toolchain.sh

@@ -546,6 +546,7 @@ while [ -n "$1" ]; do
 
 		--config)
 			if probe_cc; then
+				probe_libc
 				print_config "$1"
 				exit $?
 			fi