fftools: use fopen_utf8 to open FFREPORT

Should fix #11240

fftools/opt_common.c

@@ -23,6 +23,7 @@
 #include <stdio.h>
 
 #include "cmdutils.h"
+#include "fopen_utf8.h"
 #include "opt_common.h"
 
 #include "libavutil/avassert.h"
@@ -1204,7 +1205,7 @@ int init_report(const char *env, FILE **file)
     if (!envlevel)
         report_file_level = FFMAX(report_file_level, prog_loglevel);
 
-    report_file = fopen(filename.str, "w");
+    report_file = fopen_utf8(filename.str, "w");
     if (!report_file) {
         int ret = AVERROR(errno);
         av_log(NULL, AV_LOG_ERROR, "Failed to open report \"%s\": %s\n",