When trying to emerge the latest autogenerated version 3.7.4, I hit a missing dependency issue: cmake stops with the following error message:

CMake Error at src/gui/CMakeLists.txt:3 (find_package):
  By not providing "FindKF5Archive.cmake" in CMAKE_MODULE_PATH this project
  has asked CMake to find a package configuration file provided by
  "KF5Archive", but CMake did not find one.

  Could not find a package configuration file provided by "KF5Archive" with
  any of the following names:

    KF5ArchiveConfig.cmake
    kf5archive-config.cmake

  Add the installation prefix of "KF5Archive" to CMAKE_PREFIX_PATH or set
  "KF5Archive_DIR" to a directory containing one of the above files.  If
  "KF5Archive" provides a separate development package or SDK, be sure it has
  been installed.

I think that the package it's asking for is kde-frameworks/karchive and, considering that it is a kde package, it should probably be made optional, depending on the state of the kde USE flag.

The fact that it fails also makes me think that there can be more, possibly quite substantial changes in this new version that need to be well understood so that the autogen template can be edited accordingly.

I haven't investigated any further than just trying to emerge it and getting greeted by the error message above, so I can't give more details on what specifically needs to be done.