triggers: Add trigger flag/bool property to disable trigger during boulder buildroot preparation

[ermo]

Packages pulling in the man-db package will currently fail with an inscrutable error message that looks roughly like this:

Error: build: build recipe: root: moss client: install: client: postblit: container: exited with failure: run: io: No such file or directory (os error 2)

The error happens when the man-db trigger attempts to run a command via systemd-run on a buildroot that doesn't have a full systemd instance running.

It is worth noting that, in this specific case, there's no value in actually running the man-db system trigger, because said trigger is there only to regenerate apropos and whatis DBs under /var/cache/, which is completely irrelevant in the context of setting up a boulder buildroot.

[irevoire]

Hey!

I encountered this issue while setting up a package for shfmt.
What I found strange is that the podman recipe depends on man and still works. Is there a workaround that I missed?

The podman recipe that I just buld while writing this message: https://github.com/AerynOS/recipes/blob/main/p/podman/stone.yaml
And here's my recipe, if you add binary(man) in the builddependencies it fail with the error you described. aerynOS/recipes@main...irevoire:recipes:add-shfmt

[irevoire]

Apparently the workaround is to depends on "pkgconfig(dbus-1)".
cf https://github.com/AerynOS/recipes/pull/2036/changes