message: Fix cable CMake error message when built as a subdirectory
diff: @@ -42,7 +42,7 @@ macro(cable_set_build_type)
  endif()
  message(STATUS "Build type: ${CMAKE_BUILD_TYPE}")
  endif()
  - elseif(PROJECT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR) # After the main project().
  + elseif(PROJECT_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR) # After the main project().
  message(FATAL_ERROR "cable_set_build_type() must be used before project()")
  endif() # Sub-project - silently ignore.
  endmacro()
  