message: should link properly on linux/osx
diff: @@ -12,6 +12,8 @@ set_property(GLOBAL PROPERTY USE_FOLDERS ON)
  enable_testing()
  +find_package(Threads)
  +
  set(DOCTEST_TEST_MODE "COMPARE" CACHE STRING "Test mode - normal/run through valgrind/collect output/compare with output")
  set_property(CACHE DOCTEST_TEST_MODE PROPERTY STRINGS "NORMAL;VALGRIND;COLLECT;COMPARE")
  @@ -61,6 +63,7 @@ endfunction()
  function(doctest_add_executable name)
  add_executable(${name} ${ARGN})
  add_dependencies(${name} assemble_single_header)
  + target_link_libraries(${name} ${CMAKE_THREAD_LIBS_INIT})
  endfunction()
  function(doctest_add_library name)
  