udev-cache: strip timestamps on extract

udev-cache: strip timestamps on extract

Under normal udev operation, device nodes are obviously timestamped
based on the system time at current boot. However, when using
udev-cache, they are timestamped from a previous boot.

The existence of machines lacking RTCs makes this more than a cosmetic
issue: if the current time is set further on in the boot, so that the
system time is still 1970 by the time the cache is extracted, tar will
print a timestamp warning for every extracted file (potentially hundreds
of them).

To fix, use -m on extract.

If using busybox `tar`, this commit requires
CONFIG_FEATURE_TAR_NOPRESERVE_TIME=y.

(From OE-Core rev: b31f8f1f053cdfa9428e3f667c05e7e2c600061e)

Signed-off-by: Richard Tollerton <rich.tollerton@ni.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>