Unknown type name 'wint_t' when targeting Cygwin

[Markus Mützel]

Dear gnulib maintainers,

We recently updated gnulib to a newer revision in GNU Octave (currently 
92d80242ad1344b5364ca9bd1d995d68c3a73ef7).

Since then we are seeing compilation errors like the following when targeting 
Cygwin:

In file included from /usr/include/sys/reent.h:16,
                 from /usr/include/wchar.h:6,
                 from ./wchar.h:80,
                 from /usr/include/uchar.h:5,
                 from ./uchar.h:45,
                 from ../../libgnu/btoc32.c:23:
/usr/include/sys/_types.h:167:5: error: unknown type name 'wint_t'
  167 |     wint_t __wch;
      |     ^~~~~~

Is this because something is missing in gnulib? Are we doing something wrong?

I can try to provide logs and more information if needed.

Markus