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/core/fuzz-unit-file.c

@@ -21,7 +21,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
         const char *name;
         long offset;
 
-        if (size > 65536)
+        if (outside_size_range(size, 0, 65536))
                 return 0;
 
         f = data_to_file(data, size);