The following is a breakdown of the commands in CMakeLists.txt:

1. First, we need to define the project and detect the Python interpreter, as follows:

cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
  
project(recipe-03 LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_EXTENSIONS OFF)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(PythonInterp QUIET REQUIRED)

2. We decided to place the to-be-generated code under ${CMAKE_CURRENT_BINARY_DIR}/generated, and we need to instruct CMake to create this directory:

file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/generated)

3. The Python script expects an upper bound for the prime numbers, and, with the following command, we can set a default:

set(MAX_NUMBER "100" CACHE STRING "Upper bound for primes")

4. Next, we define a custom command to generate the header file:

add_custom_command(
  OUTPUT
    ${CMAKE_CURRENT_BINARY_DIR}/generated/primes.hpp
  COMMAND
    ${PYTHON_EXECUTABLE} generate.py ${MAX_NUMBER} ${CMAKE_CURRENT_BINARY_DIR}/generated/primes.hpp
  WORKING_DIRECTORY
    ${CMAKE_CURRENT_SOURCE_DIR}
  DEPENDS
    generate.py
  )

5. Finally, we define the executable and its target, including the directory and dependency:

add_executable(example "")

target_sources(example
  PRIVATE
    example.cpp
    ${CMAKE_CURRENT_BINARY_DIR}/generated/primes.hpp
  )

target_include_directories(example
  PRIVATE
    ${CMAKE_CURRENT_BINARY_DIR}/generated
  )

6. We are now ready to test the implementation, as follows:

$ mkdir -p build
$ cd build
$ cmake ..
$ cmake --build .
$ ./example

all prime numbers up to 100: 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97