fuzzers: ignore size limits when compiled standalone

This way we can still call fuzzers on old samples, but oss-fuzz will not waste
its and our time finding overly large inputs.

src/nspawn/fuzz-nspawn-settings.c

@@ -9,7 +9,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
         _cleanup_fclose_ FILE *f = NULL;
         _cleanup_(settings_freep) Settings *s = NULL;
 
-        if (size > 65536)
+        if (outside_size_range(size, 0, 65536))
                 return 0;
 
         f = data_to_file(data, size);