The warnings are:

oe_ei_encode_string.c:26:3: warning: expression result unused [-Wunused-value]
  (int) ei_encode_string(0,&size,p);
  ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~

oe_ei_encode_port.c:26:3: warning: expression result unused [-Wunused-value]
  (int) ei_encode_port(NULL, &size, p);
  ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

oe_ei_encode_atom.c:26:3: warning: expression result unused [-Wunused-value]
  (int) ei_encode_atom(0,&size,p);
  ^     ~~~~~~~~~~~~~~~~~~~~~~~~~

oe_ei_encode_pid.c:26::3: warning: expression result unused [-Wunused-value]
  (int) ei_encode_pid(NULL, &size, p);
  ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

oe_ei_encode_ref.c:26:3: warning: expression result unused [-Wunused-value]
  (int) ei_encode_ref(NULL, &size, p);
  ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

oe_ei_encode_term.c:26:3: warning: expression result unused [-Wunused-value]
  (int) ei_encode_term(NULL, &size, t);
  ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

in order to be backward compatible with user code that
accesses the members of erlang_pid and friend.

The documentation does not mention the content of these structs,
but we have example code that does. So the safe way it the revert
the node_org_enc field (added in R16A) and instead determine in
runtime which atom encoding to use depending on if the node atom
contains unicode (>255) characters or not.

Note that all these changes was needed due to violations of the APIs
in erl_interface and jinterface.
One might of course argue that these violations was made due to
shortages in erl_interface and jinterface.

With silent rules, the output of make is less verbose and compilation
warnings are easier to spot. Silent rules are disabled by default and
can be disabled or enabled at will by make V=0 and make V=1.