diff -Naur wesnoth-upstream-1.8.5/m4/boost.m4 wesnoth-1.8.5/m4/boost.m4

Libtools seems to set a variable called acl_libext while the Boost
library check code uses a variable called libext.  This patch makes
the Boost check use the variable acl_libext actually set by libtools.

--- wesnoth-upstream-1.8.5/m4/boost.m4	2010-10-02 20:35:59.577619372 -0430
+++ wesnoth-1.8.5/m4/boost.m4	2010-10-02 20:39:10.383653233 -0430
@@ -252,8 +252,8 @@
   test -n "$boost_rtopt" && boost_rtopt="-$boost_rtopt"
   $boost_guess_use_mt && boost_mt=-mt
   # Look for the abs path the static archive.
-  # $libext is computed by Libtool but let's make sure it's non empty.
-  test -z "$libext" &&
+  # $acl_libext is computed by Libtool but let's make sure it's non empty.
+  test -z "$acl_libext" &&
     AC_MSG_ERROR([the libext variable is empty, did you invoke Libtool?])
   boost_save_ac_objext=$ac_objext
   # Generate the test file.
@@ -309,7 +309,7 @@
       # Are we looking for a static library?
       case $boost_ldpath:$boost_rtopt_ in #(
         *?*:*s*) # Yes (Non empty boost_ldpath + s in rt opt)
-          Boost_lib_LIBS="$boost_ldpath/lib$boost_lib.$libext"
+          Boost_lib_LIBS="$boost_ldpath/lib$boost_lib.$acl_libext"
           test -e "$Boost_lib_LIBS" || continue;; #(
         *) # No: use -lboost_foo to find the shared library.
           Boost_lib_LIBS="-l$boost_lib";;