kdev-ruby's CMakeFile.txt requires weird stuff like KF5Config.cmake - cmake

Question

I'm trying to compile a Ruby plugin for KDevelop: https://github.com/KDE/kdev-ruby
When I cut a folder called build, cd build, and run cmake .., I get lots of errors:
CMake Error at CMakeLists.txt:13 (include):
include could not find load file:
KDEInstallDirs
CMake Error at CMakeLists.txt:14 (include):
include could not find load file:
KDECMakeSettings
CMake Error at CMakeLists.txt:15 (include):
include could not find load file:
KDECompilerSettings
CMake Error at CMakeLists.txt:16 (include):
include could not find load file:
ECMQtDeclareLoggingCategory
CMake Error at CMakeLists.txt:24 (find_package):
By not providing "FindKF5.cmake" in CMAKE_MODULE_PATH this project has
asked CMake to find a package configuration file provided by "KF5", but
CMake did not find one.
Could not find a package configuration file provided by "KF5" (requested
version 5.15.0) with any of the following names:
KF5Config.cmake
kf5-config.cmake
Add the installation prefix of "KF5" to CMAKE_PREFIX_PATH or set "KF5_DIR"
to a directory containing one of the above files. If "KF5" provides a
separate development package or SDK, be sure it has been installed.
How, on Ubuntu, do I install something that provides KF5Config.cmake? Preferably without rebuilding KDevelop or KDE or Qt5.

Answer 1

KDevelop relies on the development headers for various libraries, and finds them via the accompanying CMake files.
The build also uses CMake modules provided by the extra-cmake-modules package.
You must install that and libkf5config-dev.
The apt-file command might help you find the relevant packages for your distro in these situations.