Remove files generated during fuzzing of flac tool

CI-Fuzz occassionally runs out of disk space, and there might be
other problems (coverage suddenly vanishing for example) related
to disk space issues. This commit should make sure all files
generated by the flac tool are removed as soon as they are closed.

src/flac/analyze.c

@@ -245,5 +245,8 @@ FLAC__bool dump_stats(const subframe_stats_t *stats, const char *filename)
 	fprintf(outfile, "pause -1 'waiting...'\n");
 
 	fclose(outfile);
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+	unlink(filename);
+#endif
 	return true;
 }

src/flac/decode.c

@@ -297,7 +297,11 @@ void DecoderSession_destroy(DecoderSession *d, FLAC__bool error_occurred)
 		}
 #endif
 		fclose(d->fout);
+
+#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+	/* Always delete output file when fuzzing */
 		if(error_occurred)
+#endif
 			flac_unlink(d->outfilename);
 	}
 }

src/flac/encode.c

@@ -1626,6 +1626,11 @@ int EncoderSession_finish_ok(EncoderSession *e, int info_align_carry, int info_a
 		ret = 1;
 	}
 
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+        /* Always delete output file when fuzzing */
+	flac_unlink(e->outfilename);
+#endif
+
 	EncoderSession_destroy(e);
 
 	return ret;