libtool.m4: update GNU/Hurd test from upstream.  In upstream libtool, 47a889a4ca20 ("Improve GNU/Hurd support.") fixed detection of shlibpath_overrides_runpath, thus avoiding unnecessary relink.  This backports it.

.	* libtool.m4: Match gnu* along other GNU systems.

*/ChangeLog:

	* configure: Re-generate.