Building Diffutils with MinGW

Hi,

I'm building Diffutils 3.2 with MinGW, and I see this in src/system.h:

  /* This section contains POSIX-compliant defaults for macros
     that are meant to be overridden by hand in config.h as needed.  */

  #ifndef file_name_cmp
  # define file_name_cmp strcmp
  #endif

  [...]

  #ifndef NULL_DEVICE
  # define NULL_DEVICE "/dev/null"
  #endif

  [...]

  #ifndef same_file
  # define same_file(s, t) \
      ((((s)->st_ino == (t)->st_ino) && ((s)->st_dev == (t)->st_dev)) \
       || same_special_file (s, t))
  #endif

However, no tests are made by the configure script for these features,
and consequently no definitions for these macros are put into
lib/config.h after running configure.  Am I missing something?

If I don't miss anything, what would be the best way of fixing this?
I can supply the definitions needed for MinGW, but where to put them?

TIA