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

On fedora 20 64bits host, the file /usr/share/config.site contains
a fix for installing libraries into /lib/lib64 on 64bits systems
that redefine libdir in the generated Makefile.

This causes the bug 7262 reported Normen Bolling.

Set CONFIG_SITE to "no" to not use config.site

fixes: https://bugs.busybox.net/show_bug.cgi?id=7262



Reported-by: Normen Bolling <normen.bolling@teufel.de>
Cc: Normen Bolling <normen.bolling@teufel.de>
Cc: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Tested-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>