fadvise need not be mandatory.

It is just a hint, after all, so it is not an error if it is unavailable.

Author: 3405691582

src/io.c

@@ -2308,7 +2308,7 @@ _dispatch_operation_advise(dispatch_operation_t op, size_t chunk_size)
 		default: (void)dispatch_assume_zero(err); break;
 	}
 #else
-#error "_dispatch_operation_advise not implemented on this platform"
+	(void)err;
 #endif // defined(F_RDADVISE)
 #endif // defined(_WIN32)
 }