urweb installation: call 'apt-get' so that it doesn't wait for keyboard confirmation

frameworks/Ur/urweb/setup.sh

@@ -5,7 +5,7 @@ COMPILER=${IROOT}/urweb
 
 RETCODE=$(fw_exists ${COMPILER}.installed)
 [ "$RETCODE" == 0 ] || { \
-  sudo apt-get install mlton
+  sudo apt-get --assume-yes install mlton
   cd $IROOT
   fw_get -O http://www.impredicative.com/ur/urweb-$VERSION.tgz
   fw_untar urweb-$VERSION.tgz