IDE plugins should produce a functional workspace when there are included builds that do not apply the same IDE plugin

Not every team uses the same set of IDEs. Currently, a team has to encode the IDEs that are supported for their developers into their build (this is a separate issue). When multiple builds are composed into a composite, it is possible that the builds in the composite do not agree on which IDEs should be available. Essentially, only the intersection of the sets of IDEs is available, and this can easily not include the developer's choice of IDE. It _is_ possible to workaround this with an init script, but this is awkward.

"IDE plugin" means all of the IDE plugins, not just the native IDE plugins.

The issue names no files, tests, or entry points. Start by locating the composite-build handling for IDE plugins and determine how included builds contribute their supported plugins. Done should be defined as producing a functional workspace when included builds use different IDE plugin sets, including non-native IDE plugins.

Written by the indexing model from the issue text.