util/crossgcc: Add date to the toolchain revision

util/crossgcc: Add date to the toolchain revision

With the current version method, it's not possible to determine if
a different version is older or newer than the current version without
digging into the repository and finding the dates for the version
numbers.

This change adds the commit date to the start of the toolchain version
which will let us tell at a glance how old or new the toolchain is.

It's not perfect because multiple toolchain commits can go in on the
same day, but adding the time made the string even longer, and really
doesn't help that much.

Signed-off-by: Martin Roth <martin@coreboot.org>
Change-Id: I9c6d27667b922dc15e7a6e132e1beff69eed839c
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48901
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>