This patch introduces the SOURCE_DATE_EPOCH environmental variable. All files
in a package are adjusted to have their modification dates set to the value
of SOURCE_DATE_EPOCH, which defaults to "date +%s".
Setting this variable allows a package that is built twice in the same
environment to be (potentially) reproducible in that the checksum of the
generated package file will be the same.
Also adjust the compression of the mtree file to avoid gzip embedding a
timestamp.
Signed-off-by: Levente Polyak <anthraxx@archlinux.org>
d30878763c