Fix an error in selecting encoding when writing zip files

* lisp/international/mule-cmds.el (select-safe-coding-system):
Treat no-conversion-multibyte that came from find-auto-coding
the same as no-conversion for the purposes of encoding.  The
same logic that considers no-conversion always safe should do
the same with no-conversion-multibyte.  (Bug#38155)
1 job for master in 90 minutes and 1 second (queued for 2 seconds)
Status Job ID Name Coverage
failed #4162


Name Stage Failure
test-all Test The script exceeded the maximum execution time set for the job
  GEN      lisp/international/ccl-tests.log
ELC lisp/international/mule-tests.elc
GEN lisp/international/mule-tests.log
ELC lisp/international/mule-util-tests.elc
GEN lisp/international/mule-util-tests.log
ELC lisp/international/ucs-normalize-tests.elc
GEN lisp/international/ucs-normalize-tests.log
Pulling docker image gitlab/gitlab-runner-helper:x86_64-d0b76032 ...
ERROR: Job failed: execution took longer than 1h30m0s seconds