unix: make minimal #1688

$ make minimal
...
CC ../py/objattrtuple.c
In file included from ../py/objtuple.h:29:0,
                 from ../py/objattrtuple.c:27:
../py/obj.h:440:57: error: unknown type name ‘uintptr_t’
     mp_uint_t (*ioctl)(mp_obj_t obj, mp_uint_t request, uintptr_t arg, int *errcode);
                                                         ^
make[1]: *** [build-minimal/py/objattrtuple.o] Error 1
make[1]: Leaving directory `'
make: *** [minimal] Error 2