[egs] TIMIT: fix mac compatibility of sed command (#2874)

egs/timit/s5/local/timit_data_prep.sh

@@ -70,7 +70,7 @@ for x in train dev test; do
  find $*/{$train_dir,$test_dir} -not \( -iname 'SA*' \) -iname '*.WAV' \
  | grep -f $tmpdir/${x}_spk > ${x}_sph.flist
 
- sed -e 's:.*/\(.*\)/\(.*\).WAV$:\1_\2:i' ${x}_sph.flist \
+ sed -e 's:.*/\(.*\)/\(.*\).WAV$:\1_\2:' ${x}_sph.flist \
  > $tmpdir/${x}_sph.uttids
  paste $tmpdir/${x}_sph.uttids ${x}_sph.flist \
  | sort -k1,1 > ${x}_sph.scp
@@ -82,7 +82,7 @@ for x in train dev test; do
  # ID followed by the transcript.
  find $*/{$train_dir,$test_dir} -not \( -iname 'SA*' \) -iname '*.PHN' \
  | grep -f $tmpdir/${x}_spk > $tmpdir/${x}_phn.flist
- sed -e 's:.*/\(.*\)/\(.*\).PHN$:\1_\2:i' $tmpdir/${x}_phn.flist \
+ sed -e 's:.*/\(.*\)/\(.*\).PHN$:\1_\2:' $tmpdir/${x}_phn.flist \
  > $tmpdir/${x}_phn.uttids
  while read line; do
  [ -f $line ] || error_exit "Cannot find transcription file '$line'";