cwautomacros: Ensure version is set deterministically

The makefile injects the current date into the version file. Do this
deterministically with SOURCE_DATE_EPOCH.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 31f2ad73)
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>