avutil/file_open: Print debug message if setting close on exec fails

Fixes CID1087079
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/file_open.c

@@ -85,8 +85,10 @@ int avpriv_open(const char *filename, int flags, ...)
 
     fd = open(filename, flags, mode);
 #if HAVE_FCNTL
-    if (fd != -1)
-        fcntl(fd, F_SETFD, FD_CLOEXEC);
+    if (fd != -1) {
+        if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
+            av_log(NULL, AV_LOG_DEBUG, "Failed to set close on exec\n");
+    }
 #endif
 
     return fd;