I would not distinguish between self-builds and buildbot builds. There are extcap developers out there, who use the released Wireshark version to develop extcap interfaces and also would benefit greatly from using such debug scenarios. And I would not want to tell them to explicitly build a development version, just to develop an extcap. More specifically, if they develop the extcap with Python, they may not even be able easily to build Wireshark at all.
On the other side, not every dev wants to see the debug functionality for extcap, so having those users stuck with debug output may also not be advisable.
Last, some issues can come up, especially with printf stuff, where debug outputs actually hinder development. If you have a timing-constraint related bug, it may not appear in a debug version, because the debug code may slow down the utility enough, so that the issue may not appear, but it would appear in the release version. Not every developer thinks of such a thing and would end up hunting bugs they cannot see.
So, please do integrate such a feature in the normal code, but make it configurable via preference for instance, to enable/disable the functionality. Do not distinguish, if it is a dev-build or release build
cheers
Roland