Build fails when using -Pscala-2.12

Build fails on assembly module due to scala-2.11 dependencies.
I think this is due to the `${scala.binary.version}` being used in the `modules` sections, and it's populated before the profiles are loaded.
When I ensure that scala-2.12 is the default in the `` then it works fine.

Start by reproducing the build failure with the -Pscala-2.12 profile, focusing on the assembly module and its scala-2.11 dependencies. Read the modules sections, the scala.binary.version property, and the profile-loading configuration to trace when the value is populated. Done means assembly succeeds with -Pscala-2.12 and uses Scala 2.12 dependencies.

Written by the indexing model from the issue text.