Allow to override build date with SOURCE_DATE_EPOCH
Allow to override build date with SOURCE_DATE_EPOCH

in order to make builds reproducible.
See https://reproducible-builds.org/ for why this is good
and https://reproducible-builds.org/specs/source-date-epoch/
for the definition of this variable.

This renames BUILD_INFO to the standard name
so that distributions do not have to discover the BUILD_INFO variable.

Signed-off-by: Bernhard M. Wiedemann <244367295b3bb774ff9b9118e48bfb695d6a3881@suse.de>

kubernetes-incubator/ocid,kubernetes-incubator/cri-o,kubernetes-incubator/cri-o,kubernetes-incubator/cri-o,mikebrow/cri-o,kubernetes-incubator/ocid,kubernetes-incubator/ocid,mikebrow/cri-o,mikebrow/cri-o,nalind/cri-o,kubernetes-incubator/cri-o,nalind/cri-o,mikebrow/cri-o,nalind/cri-o