tools/target_dec_fuzzer: enable mjpeg for tiff or tdsc

This is needed for fuzzing tiff/tdsc and should increase coverage
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/allcodecs.c

@@ -812,6 +812,7 @@ extern AVCodec ff_vp9_qsv_encoder;
 // The iterate API is not usable with ossfuzz due to the excessive size of binaries created
 #if CONFIG_OSSFUZZ
 AVCodec * codec_list[] = {
+    NULL,
     NULL,
     NULL
 };

tools/target_dec_fuzzer.c

@@ -120,6 +120,12 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
         codec_list[0] = &DECODER_SYMBOL(FFMPEG_DECODER);
         avcodec_register(&DECODER_SYMBOL(FFMPEG_DECODER));
 
+#if FFMPEG_DECODER == tiff || FFMPEG_DECODER == tdsc
+        extern AVCodec DECODER_SYMBOL(mjpeg);
+        codec_list[1] = &DECODER_SYMBOL(mjpeg);
+        avcodec_register(&DECODER_SYMBOL(mjpeg));
+#endif
+
         c = &DECODER_SYMBOL(FFMPEG_DECODER);
 #else
         avcodec_register_all();