libxpm: Fixed cross compilation by passing the right LIBTOOL on $makeopt

xorg/libxpm/libxpm.conf

@@ -0,0 +1,17 @@
+# --- SDE-COPYRIGHT-NOTE-BEGIN ---
+# This copyright note is auto-generated by ./scripts/Create-CopyPatch.
+#
+# Filename: package/.../libxpm/libxpm.conf
+# Copyright (C) 2008 The OpenSDE Project
+#
+# More information can be found in the files COPYING and README.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License. A copy of the
+# GNU General Public License can be found in the file COPYING.
+# --- SDE-COPYRIGHT-NOTE-END ---
+
+if atstage cross; then
+	var_append makeopt ' ' "LIBTOOL=$LIBTOOL"
+fi