make max time constant relative to min compile time

tlsdate has been hardcoding 18 May 2033 as the max valid time it will
accept.  This has been "really far in the future", but it's now less
than 10 years away.  Let's change the max valid time to be relative to
the min compile time that we already enforce.

For now, set the window to 15 years.  This matches platform2/init.

BUG=b:307794426
TEST=CQ passes

Change-Id: Ia24464a52dd50491722aefa73133577f5c037910
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/tlsdate/+/4978700
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Pavol Marko <pmarko@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
1 file changed