Does it make sense to add build-time secrets directly to a builder app?

Questions / Help
4

There’s the flyctl deploy -e <k=v> switch to overwrite envs, though, I’m unsure if it is available insider docker (during build). If it is, then that’s one possible avenue to inject DATABASE_URL at build-time and runtime.

Note though, flyctl overwrites all envs set via fly.toml rather than selectively override them: Is it possible to combine both env vars from CLI flags and fly.toml config?