klauncher uses CMAKE_INSTALL_FULL_LIBEXECDIR_KF5 on Windows and Mac to find kioslave executable (see https://cgit.kde.org/kinit.git/tree/src/klauncher/klauncher.cpp#n1072 and https://cgit.kde.org/kinit.git/tree/src/klauncher/klauncher.cpp#n1098). This does not work at least on Windows where the runtime path of kioslave.exe does not match the compile time path Because on Windows kioslave.exe lives in the same directory as klauncher and the Windows api searches in this directory the solution is to remove any path from the requested executable string and let KProcess find it.
review request https://phabricator.kde.org/D7707