prelude-lml: Use the correct location for libprelude while cross-compiling

Note: Nevertheless prelude-lml is not cross-compilable yet because the
      configure script doesn't allow yet to specifiy the correct pcre prefix!

security/prelude-lml/prelude-lml.conf

@@ -2,6 +2,7 @@
 # This copyright note is auto-generated by ./scripts/Create-CopyPatch.
 #
 # Filename: package/.../prelude-lml/prelude-lml.conf
+# Copyright (C) 2008 The OpenSDE Project
 # Copyright (C) 2004 - 2006 The T2 SDE Project
 #
 # More information can be found in the files COPYING and README.
@@ -19,3 +20,7 @@ if [ $prefix_auto = 1 ] ; then
         fi
         set_confopt
 fi
+
+# use the correct location for libprelude while cross-compiling
+pkgprefix -t libprelude
+var_append extraconfopt ' ' "--with-libprelude-prefix=$root/$( pkgprefix libprelude )"