gitlab-ci: Append /usr/bin/*_perl to PATH

Under archlinux-based container runs, non-login shells need to source
/etc/profile to have package-specific commands such as encguess (under
/usr/bin/core_perl) appended in its PATH.

Add the command so that the change in commit 00361e8bb1e5 ("Convert
*.log files into UTF-8 encoding") to work in gitlab-ci builds.

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Leonardo Bras <lsoaresp@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>