fate: Work around non-standard wc implementations at more places

This applies the same fix as in ed7409fe for lavf-regressions.sh.
Signed-off-by: Martin Storsjö <martin@martin.st>

tests/lavf-regression.sh

@@ -33,7 +33,7 @@ do_image_formats()
     run_avconv $DEC_OPTS -f image2 -vcodec pgmyuv -i $raw_src $2 $ENC_OPTS $3 -t 0.5 -y -qscale 10 $target_path/$file
     do_md5sum ${outfile}02.$1
     do_avconv_crc $file $DEC_OPTS $3 -i $target_path/$file
-    wc -c ${outfile}02.$1
+    echo $(wc -c ${outfile}02.$1)
 }
 
 do_audio_only()