Revert "package/localedef: don't use config.site when cross-compiling"

CONFIG_SITE is now a part of pkg-autotools infrastructure.

This reverts commit 85448feb.

Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Acked-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>