configure: work around bug in ash shell

The ash 'test' builtin misbehaves if the first operand of a binary
operator looks like a unary operator.
Signed-off-by: Mans Rullgard <mans@mansr.com>

configure

@@ -593,7 +593,7 @@ print_config(){
 }
 
 print_enabled(){
-    test "$1" = -n && end=" " && shift || end="\n"
+    test x"$1" = x-n && end=" " && shift || end="\n"
     suf=$1
     shift
     for v; do