golang-vcs-snapshot: Update to upstream

Update the golang-vcs-snapshot eclass to the latest version from gentoo.
We need this because the lxd ebuild uses some new features from this
eclass.

BUG=chromium:786657
TEST=emerge-tatl lxd

Change-Id: I377b0476c7ca557b5be4da2730b55f59951a700d
Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/784270
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed