Auto-generate files after cl/563149248

ruby/ext/google/protobuf_c/ruby-upb.h

diff --git a/ruby/ext/google/protobuf_c/ruby-upb.h b/ruby/ext/google/protobuf_c/ruby-upb.h
index 829ddf0..4f84326 100755
--- a/ruby/ext/google/protobuf_c/ruby-upb.h
+++ b/ruby/ext/google/protobuf_c/ruby-upb.h
@@ -2000,6 +2000,8 @@
 #ifndef UPB_MESSAGE_MESSAGE_H_
 #define UPB_MESSAGE_MESSAGE_H_
 
+#include <stddef.h>
+
 
 // Must be last.