Building samples fails

[asasine]

Building the samples fails with a missing file increment.cpp. Steps to reproduce:

git clone https://github.com/BehaviorTree/BehaviorTree.CPP.git
cd BehaviorTree.CPP
mkdir build
cd build
cmake .. -DBUILD_SAMPLES=ON

CMake output:

-- Found boost::coroutine2.
-- ZeroMQ found.
-- BEHAVIOR_TREE_LIB_DESTINATION:   lib
-- BEHAVIOR_TREE_BIN_DESTINATION:   bin
-- CMAKE_RUNTIME_OUTPUT_DIRECTORY:  /home/adam/src/BehaviorTree.CPP/build/bin
-- CMAKE_LIBRARY_OUTPUT_DIRECTORY:  /home/adam/src/BehaviorTree.CPP/build/lib
-- CMAKE_ARCHIVE_OUTPUT_DIRECTORY:  /home/adam/src/BehaviorTree.CPP/build/bin
-- Configuring done
CMake Error at examples/CMakeLists.txt:56 (add_executable):
  Cannot find source file:

    increment.cpp

  Tried extensions .c .C .c++ .cc .cpp .cxx .m .M .mm .h .hh .h++ .hm .hpp
  .hxx .in .txx


CMake Error: CMake can not determine linker language for target: increment
CMake Error: Cannot determine link language for target "increment".
-- Generating done
-- Build files have been written to: /home/adam/src/BehaviorTree.CPP/build