I've seen several projects where the build rewrites some part of the code to generate a custom binary for each target environment. This always seems to make things much more complicated than they need be, and introduces a risk that the team may not have consistent versions on each box. At a minimum it involves building multiple, near-identical copies of the software which then have to be deployed to the right places. It means more moving parts than necessary, which means more opportunities to make a mistake. I've worked on a team where every change had to be checked in for a full build cycle, which meant that our testers were left waiting whenever they needed a minor setting adjustment. I've worked on a team where the system administrators insisted on rebuilding from scratch for production, which meant that we had no proof that the version in production was the one that had been through testing. And so on.
The rule is simple. Build a single binary that you can identify and promote through all the stages in the release pipeline. Hold environment-specific details in the environment in, for example, the component container settings, a known file, or the path. Of course there are exceptions, say where you're building for targets that have significantly different resource constraints, but they don't apply to the majority of us who are writing "database to screen and back again" applications. If you do have a code-mangling build, then it suggests that either the team hasn't thought through its design enough to figure out which parts of the system move where or, worse, that the team has but cannot find the time to make the changes.
And one more thing: Keep the environment information versioned too. Some teams like to keep the settings in the same repository as the code; some like a different repository. There are advantages to both.
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