shopt -s xpg_echo is not propagated anymore in subshell

Issue

• When switching the bash option xpg_echo with shopt, a new script does not inherit of the setting.

• For example:

  $ cat a.sh :
  shopt -s xpg_echo
  echo "\t 1st test"
  ./b.sh
  
  $ cat b.sh
  echo "\t 2nd test"
  

• The output is:

           1st test
  \t 2nd test
  

=> in second script, \t is not interpreted as tabulation.

• In RHEL 7, the echo of \t from second script is interpreted (if we add shopt -p xpg_echo, we ca see the value of the option):

           1st test
  shopt -s xpg_echo
           2nd test