reproducible_build_simple.bbclass: simple environment for reproducible binaries

reproducible_build_simple.bbclass: simple environment for reproducible binaries

Export environmental variables needed for binary reproducibility with consistent values.

This class can be used either directly via:
INHERIT += "reproducible_build_simple"

or can be inherited by a more complex/complete bbclass, for example a bblass which
will crack SOURCE_DATE_EPOCH for each recipe.

(From OE-Core rev: 5c2685c5ee2f8210a36b9a8591491b6af0482084)

Signed-off-by: Juro Bystricky <juro.bystricky@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>