fuzzer_load: disallow include option in config files

It produces undeterministic results, especially if it do
`include=fd://N` which starts loading external data.

fuzzers/fuzzer_load.c

@@ -28,6 +28,11 @@
 
 int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 {
+#if defined(MPV_LOAD_CONFIG_FILE) || defined(MPV_LOAD_INPUT_CONF)
+    if (memmem(data, size, "include", sizeof("include") - 1))
+        return 0;
+#endif
+
     // fmemopen doesn't have associated file descriptor, so we do copy.
     int fd = memfd_create("fuzz_mpv_load", 0);
     if (fd == -1)