trees: err if no argument given

We were already covering this from the main build
script, but it's good to also check it here.

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/trees

@@ -24,6 +24,8 @@ mode="all" # make all
 
 main()
 {
+	[ $# -lt 1 ] && $err "No argument provided"
+
 	while getopts f:b:m:u:c:x:s:l:n:d: option; do
 		[ -n "$_f" ] && $err "only one flag is permitted"
 		_f="$1"