rabbit_upgrade_functions: Turn off export_all warning

Erlang 20.x warns if `export_all` is set in a module by default. We need
to turn the warning off.

Author: dumbbell

src/rabbit_upgrade_functions.erl

@@ -19,7 +19,7 @@
 %% If you are tempted to add include("rabbit.hrl"). here, don't. Using record
 %% defs here leads to pain later.
 
--compile([export_all]).
+-compile([nowarn_export_all, export_all]).
 
 -rabbit_upgrade({remove_user_scope,     mnesia, []}).
 -rabbit_upgrade({hash_passwords,        mnesia, []}).