Fails to compile on Ubuntu 18.04.2

[sdwfrost]

Hi @bingmann

I get the following errors when trying to compile (using g++-7):

CMake Error at CMakeLists.txt:87 (add_subdirectory):
  The source directory

    /home/simon/Programs/cobs/extlib/googletest

  does not contain a CMakeLists.txt file.

CMake Error at CMakeLists.txt:94 (add_subdirectory):
  add_subdirectory given source "extlib/xxhash/cmake_unofficial" which is not
  an existing directory.

-- Found ZLIB: /usr/lib/x86_64-linux-gnu/libz.so (found version "1.2.11") 
-- Boost version: 1.65.1
-- Found the following Boost libraries:
--   system
--   filesystem
CMake Error at CMakeLists.txt:116 (add_subdirectory):
  The source directory

    /home/simon/Programs/cobs/extlib/tlx

  does not contain a CMakeLists.txt file.

CMake Error at python/CMakeLists.txt:9 (add_subdirectory):
  The source directory

    /home/simon/Programs/cobs/python/pybind11

  does not contain a CMakeLists.txt file.

CMake Error at python/CMakeLists.txt:10 (pybind11_add_module):
  Unknown CMake command "pybind11_add_module".

tlx and pybind11 are installed on my machine too.

[bingmann]

use git clone --recursive to get the submodules.

[sdwfrost]

My bad! Didn't notice the --recursive