sys-apps/portage: Bump to version 2.3.78

sys-apps/portage: Bump to version 2.3.78

 #697566 fetch: Use FETCHCOMMAND to fetch mirror layout.conf
 #697890 emirrordist: Fix DeletionTask layout assumptions
 #697906 emirrordist: Delete potential symlinks for all layouts
 #698046 make.globals: Change FETCHCOMMAND_RSYNC to --copy-links

Bug: https://bugs.gentoo.org/697734
Bug: https://bugs.gentoo.org/697566
Bug: https://bugs.gentoo.org/697890
Bug: https://bugs.gentoo.org/697906
Bug: https://bugs.gentoo.org/698046
Package-Manager: Portage-2.3.78, Repoman-2.3.17
Signed-off-by: Zac Medico <zmedico@gentoo.org>