open https://gitlab.synchro.net/main/sbbs/-/issues/661

Only seen once, that I'm aware of, on git.synchro.net:
```
2023-10-15T05:01:54.655820-07:00 git sbbs: evnt LNXBUILD Running native background timed event: LNXBUILD
2023-10-15T05:01:54.655846-07:00 git sbbs: evnt LNXBUILD Executing external: /sbbs/exec/jsexec testbuild.js -cov-token=secret
```
After I noticed no event where running on git, I recycled it:
```
2023-10-15T20:53:22.904438-07:00 git sbbs: evnt BBS Events JavaScript: Destroying context
2023-10-15T20:53:22.910952-07:00 git sbbs: evnt BBS Events JavaScript: Destroying runtime
2023-10-15T20:53:22.912066-07:00 git sbbs: evnt BBS Events BBS Events thread terminated
```
Conspicuously absent was the "Detaching external process" log message and it appears the event process (jsexec in this case) didn't actually run.

Just previous to this occurrence, a successful background execution looks like this in the log:
```
2023-10-15T04:00:00.745122-07:00 git sbbs: evnt STBUILD Running native background timed event: STBUILD
2023-10-15T04:00:00.745164-07:00 git sbbs: evnt STBUILD Executing external: /sbbs/exec/jsexec synctermbuild
2023-10-15T04:00:00.805042-07:00 git sbbs: evnt STBUILD Detaching external process
```
--- SBBSecho 3.20-Linux
* Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)