configure: fix parsing issue with more than one value per option

With commit a9c3d70d90 ("configure: add options ability") users are no
more able to provide wrong command lines like:

$ ./configure --include_dir foo bar

The script simply bails out when user provides more than one value for a
single option. However, in doing so, it breaks backward compatibility with
some packaging system, which expects unknown options to be ignored.

Commit a3272b9372 ("configure: restore backward compatibility") fix this
issue, but makes it possible again for users to provide wrong command lines
such as the one above.

This fixes the issue simply ignoring autoconf-like options such as
'--opt=value'.

Fixes: a3272b9372 ("configure: restore backward compatibility")
Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
Acked-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: David Ahern <dsahern@kernel.org>

configure

@@ -517,10 +517,12 @@ else
 				shift 2 ;;
 			-h | --help)
 				usage 0 ;;
+			--*)
+				shift ;;
 			"")
 				break ;;
 			*)
-				shift 1 ;;
+				usage 1 ;;
 		esac
 	done
 fi