Specifies the default checking style for  the  environment  file
  created  by  this  module  if  any.   The following keywords are
  supported:

     COMPILATION_TIME
       Uses the compilation time of the environment file in all
       subsequent compile-time and link-time checking for users of this
       environment file. This is the default.

     IDENT_STRING
       Uses the [IDENT()] string of the environment file in all
       subsequent compile-time and link-time checking for users of this
       environment file.

     NONE
       Disables all compile-time and link-time checking for users of
       this environment file.