buildroot

linux-advanced: Fix probing of kernel version

Probing the kernel version uses command substitution to capture the
result of a make command. If the top-level make is run with -C, the
sub-make will print entering/leaving directory messages, mucking up the
output we're trying to capture.

Invoke the sub-make with --no-print-directory so we get clean output.

Signed-off-by: Cameron Hutchison <cam@camh.ch>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>