First major #libreOps win: first worldmapper Laminar build is only failing 2/3 of the runsteps.
I had forgotten that #Laminar is flexible enough to be used to run more than just shell scripts and there's no default interpreter assumed, it just fails to execute and prints a log message. So, explicitly setting the bash interpreter in the hashbang line was necessary for the scripts to execute.
Now the other 2/3 of the fix in theory is just a copy-paste from the .before script into the .run and .after scripts.
Then time to trigger another build and see what's next to fix.