Make make_lock_file_name more robust

* src/filelock.c (make_lock_file_name): Protect against the
make-lock-file-name not being defined.
(lock_file, unlock_file_body, Ffile_locked_p): Return early if not
defined.
8 jobs for master in 18 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Prep Images
failed #22973
prep-image-base

00:00:18

 
  Build Images
skipped #22974
build-image-inotify
 
  Platform Images
skipped #22975
build-image-filenotify-gio
skipped #22976
build-image-gnustep
 
  Platforms
skipped #22977
test-filenotify-gio
skipped #22978
test-gnustep
 
  Native Comp Images
skipped #22979
build-native-bootstrap-speed0
 
  Slow
skipped #22980
test-all-inotify
 
Name Stage Failure
failed
prep-image-base Prep Images There has been a runner system failure, please try again
$ git config --global http.proxy $HTTP_PROXY; git config --global https.proxy $HTTPS_PROXY
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/emacs/emacs/.git/
From https://emba.gnu.org/emacs/emacs
* [new ref] e762864b9d501cfbc15fd20f403fc435bbdc580e -> refs/pipelines/11332
Checking out e762864b as master...

Skipping Git submodules setup
ERROR: Job failed (system failure): Error response from daemon: Conflict. The container name "/runner-2oEDrUT7-project-1-concurrent-1-build-4" is already in use by container "f46df44a43bee1f61a6ede2eac732a4e06eaa2094659f7ea23718f093d67bcc6". You have to remove (or rename) that container to be able to reuse that name. (executor_docker.go:726:0s)