ones.c:49:16: error: 'byte' redeclared as different kind of symbol
   49 | static uint8_t byte = 0xff;
      |                ^~~~
In file included from /usr/i686-w64-mingw32/sys-root/mingw/include/wtypes.h:8,
                 from /usr/i686-w64-mingw32/sys-root/mingw/include/winscard.h:10,
                 from /usr/i686-w64-mingw32/sys-root/mingw/include/windows.h:97,
                 from /usr/i686-w64-mingw32/sys-root/mingw/include/winsock2.h:23,
                 from /usr/i686-w64-mingw32/sys-root/mingw/include/ws2tcpip.h:17,
                 from ../../include/nbdkit-common.h:48,
                 from ../../include/nbdkit-plugin.h:38,
                 from ones.c:43:
/usr/i686-w64-mingw32/sys-root/mingw/include/rpcndr.h:63:25: note: previous declaration of 'byte' with type 'byte' {aka 'unsigned char'}
   63 |   typedef unsigned char byte;
      |                         ^~~~

Fixes: commit 1b13f803