10077 usr/src/uts/ Makefile changes for smatch

*** 20,29 ****
--- 20,30 ----
  #
  #
  # Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  # Use is subject to license terms.
  #
+ # Copyright (c) 2018, Joyent, Inc.
  
  #
  # This makefile drives the production of the rwd driver kernel module.
  #
  # i86pc architecture dependent
*** 65,74 ****
--- 66,78 ----
  LINTTAGS        += -erroff=E_BAD_PTR_CAST_ALIGN
  
  CERRWARN        += -_gcc=-Wno-uninitialized
  CERRWARN        += -_gcc=-Wno-unused-value
  
+ # needs work
+ SMOFF += return_cast
+ 
  #
  #       Default build targets.
  #
  .KEEP_STATE: