Issue #23573: Fix bytes.rfind() and bytearray.rfind() on Windows

Windows has no memrchr() function.

This change is only a workaround, the optimization must be reenabled on other
platforms.

Objects/bytearrayobject.c

@@ -1166,7 +1166,8 @@ bytearray_find_internal(PyByteArrayObject *self, PyObject *args, int dir)
     ADJUST_INDICES(start, end, len);
     if (end - start < sub_len)
         res = -1;
-    else if (sub_len == 1) {
+    /* Issue #23573: FIXME, windows has no memrchr() */
+    else if (sub_len == 1 && dir > 0) {
         unsigned char needle = *sub;
         int mode = (dir > 0) ? FAST_SEARCH : FAST_RSEARCH;
         res = stringlib_fastsearch_memchr_1char(

Objects/bytesobject.c

@@ -1938,7 +1938,8 @@ bytes_find_internal(PyBytesObject *self, PyObject *args, int dir)
     ADJUST_INDICES(start, end, len);
     if (end - start < sub_len)
         res = -1;
-    else if (sub_len == 1) {
+    /* Issue #23573: FIXME, windows has no memrchr() */
+    else if (sub_len == 1 && dir > 0) {
         unsigned char needle = *sub;
         int mode = (dir > 0) ? FAST_SEARCH : FAST_RSEARCH;
         res = stringlib_fastsearch_memchr_1char(