update build_support/packages.sh prompt message (#673)

update prompt

Author: mooxiu

build_support/packages.sh

@@ -21,7 +21,7 @@ main() {
     else
         echo "PACKAGES WILL BE INSTALLED. THIS MAY BREAK YOUR EXISTING TOOLCHAIN."
         echo "YOU ACCEPT ALL RESPONSIBILITY BY PROCEEDING."
-        read -p "Proceed? [Y/n] : " yn
+        read -p "Proceed? [y/N] : " yn
 
         case $yn in
             Y|y) install;;