Compiling Objective-C++ based projects

Hey there!
Lately I found myself in a tricky situation. Some parts of my project,
which is mostly based C/C++ and uses the Gradle ‘cpp-library’ plugin, must be implemented using Objective C++.
However, the C/C++ parts compile fine, but Gradle doesn’t even start compiling the ‘*.mm’-files.

Does anybody know how to compile Objective C++ files using the ‘cpp-library’?