sanity: Add warning for local hasheqiv server with remote sstate mirrors

sanity: Add warning for local hasheqiv server with remote sstate mirrors

We're seeing a lot of users configuring an sstate mirror but not realising that
the default hash equivalenve setting will make this ineffective. Add a warning
to highlight this to the user for the common case.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
(cherry picked from commit ae4eb33b5a6a037348e8f66e3d4f19b58dba8fa2)
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>