Fix typo in libtoolize error message.

[Ralf Wildenhues]

Hello,

I've pushed this trivial patch.

Cheers,
Ralf

        * libtoolize.m4sh (func_nonemptydir_p): Fix typo in error
        message.

diff --git a/libtoolize.m4sh b/libtoolize.m4sh
index b6d35f2..f74cd7c 100644
--- a/libtoolize.m4sh
+++ b/libtoolize.m4sh
@@ -1389,7 +1389,7 @@ func_nonemptydir_p ()
 
     # Is it a directory at all?
     test -d "$my_dir" \
-      || func_fatal_error "\$$my_dirvar not a directory: \`$my_dir'"
+      || func_fatal_error "\$$my_dirvar is not a directory: \`$my_dir'"
 
     # check that the directories contents can be ls'ed
     test -n "`{ cd $my_dir && ls; } 2>/dev/null`" \