10080 smatch Makefile changes for usr/src/cmd

*** 19,29 ****
  # CDDL HEADER END
  #
  # Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  # Use is subject to license terms.
  #
! # cmd/write/Makefile
  
  PROG= write
  
  include ../Makefile.cmd
  
--- 19,29 ----
  # CDDL HEADER END
  #
  # Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  # Use is subject to license terms.
  #
! # Copyright (c) 2018, Joyent, Inc.
  
  PROG= write
  
  include ../Makefile.cmd
  
*** 36,45 ****
--- 36,47 ----
  .KEEP_STATE:
  
  CFLAGS += $(CCVERBOSE)
  CERRWARN += -_gcc=-Wno-unused-variable
  
+ SMOFF += all_func_returns
+ 
  all: $(PROG)
  
  install: all $(ROOTPROG)
  
  clean: