kernel/linux: fix using custom tarball

The custom-tarball symlink was created in CT_SRC_DIR, when it
should be created in CT_TARBALLS_DIR.

Reported-by: Guylhem Aznar <crossgcc@guylhem.net>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 #!/bin/sh

 # Needed for systems without gettext

 $* -xc -o /dev/null - > /dev/null 2>&1 << EOF

 #include <libintl.h>

 int main()

 {

 	gettext("");

 	return 0;

 }

 EOF

 if [ ! "$?" -eq "0"  ]; then

 	echo -DKBUILD_NO_NLS;

 fi