Exclude UNIXSocket tests again; ref #3878

mrbgems/mruby-socket/test/unix.rb

@@ -1,3 +1,5 @@
+unless SocketTest.win?
+
 def unixserver_test_block
   path = SocketTest.tmppath
   File.unlink path rescue nil
@@ -124,3 +126,5 @@ assert('UNIXSocket#recvfrom') do
     # a[1][1] would be "" or something
   end
 end
+
+end # SocketTest.win?