Only add sys.__getattr__ on Windows

Author: XuehaiPan

Python/sysmodule.c

@@ -977,6 +977,7 @@ sys_exit_impl(PyObject *module, PyObject *status)
 // This function is used to warn about the future change of sys.abiflags
 // from absent to a meaningful value on all platforms.
 // It can be removed when the change is made.
+#ifndef ABIFLAGS
 static PyObject *
 sys___getattr__(PyObject *module, PyObject *name)
 {
@@ -997,6 +998,7 @@ PyDoc_STRVAR(__getattr___doc,
 "\n"
 "Get a sys attribute by name.\n"
 );
+#endif
 
 
 static PyObject *
@@ -2729,8 +2731,10 @@ static PyMethodDef sys_methods[] = {
     SYS_EXC_INFO_METHODDEF
     SYS_EXCEPTHOOK_METHODDEF
     SYS_EXIT_METHODDEF
+#ifndef ABIFLAGS
     {"__getattr__", _PyCFunction_CAST(sys___getattr__),
      METH_O, __getattr___doc},
+#endif
     SYS_GETDEFAULTENCODING_METHODDEF
     SYS_GETDLOPENFLAGS_METHODDEF
     SYS_GETALLOCATEDBLOCKS_METHODDEF