guess libtool-prefix and update necessary search paths.

[[Imported from SVN: r5378]]

bin/dune-autogen

@@ -22,6 +22,13 @@ rm -f $name.m4
 # add current dir to PATH
 PATH=`dirname $0`:$PATH
 
+# guess libtool prefix
+if test -n "$LIBTOOLIZE"; then
+    LIBTOOL_prefix=`dirname \`dirname $LIBTOOLIZE\``
+    PATH=$LIBTOOL_prefix:$PATH
+    ACLOCAL_FLAGS="$ACLOCAL_FLAGS -I $LIBTOOL_prefix/share/aclocal"
+fi
+
 for OPT in "$@"; do
     set +e
     # stolen from configure...