[PATCH] libtool.m4: update GNU/Hurd test from upstream

[Nick Clifton]

Hi Samuel,

> ping?

Oops - sorry.

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

Approved and applied.

Cheers
   Nick