pigz: upgraded package to upstream

Upgraded app-arch/pigz to version 2.6.

BUG=None
TEST=CQ passes

Change-Id: I8dbd33af489b472602443d74159d19deefd4eb63
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2923080
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Sergey Frolov <sfrolov@google.com>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
3 files changed