Fix cores detection for multiple single-core CPUs

Systems with multiple physical CPUs where each CPU
only has one core doesn't return the same structure as
a system with one CPU and multiple cores in that CPU.

This fixes that case.

The original code expected this structure:
1> erlang:system_info(cpu_topology).
[{processor,[{core,[{thread,{logical,0}},
                    {thread,{logical,1}}]},
             {core,[{thread,{logical,2}},{thread,{logical,3}}]},
             {core,[{thread,{logical,4}},{thread,{logical,5}}]},
             {core,[{thread,{logical,6}},{thread,{logical,7}}]}]}]

...while on some single-core (yet with multiple physical CPUs),
the result of the same function looks like:

1> erlang:system_info(cpu_topology).
[{processor,{logical,0}},{processor,{logical,1}}]

src/stdinout_pool_server.erl

@@ -36,10 +36,14 @@ count_cpus(undefined, Count) ->
   Count;
 count_cpus([], Count) ->
   Count;
-count_cpus([{node, [{processor, Cores}]} | T], Count) ->
+count_cpus([{node, [{processor, Cores}]} | T], Count) when is_list (Cores) ->
   count_cpus(T, Count + length(Cores));
-count_cpus([{processor, Cores} | T], Count) ->
-  count_cpus(T, Count + length(Cores)).
+count_cpus([{node, [{processor, _}]} | T], Count) ->
+  count_cpus(T, Count + 1);
+count_cpus([{processor, Cores} | T], Count) when is_list (Cores) ->
+  count_cpus(T, Count + length(Cores));
+count_cpus([{processor, _} | T], Count) ->
+  count_cpus(T, Count + 1).
 
 %%====================================================================
 %% gen_server callbacks