if(PROJECT_SOURCE_DIR STREQUAL PROJECT_BINARY_DIR)
    message(FATAL_ERROR
        "\n"
        "In-source builds are not allowed.\n"
        "Instead, provide a path to build tree like so:\n"
        "cmake -B <destination>\n"
        "\n"
        "To remove files you accidentally created execute:\n"
        "rm -rf CMakeFiles CMakeCache.txt\n"
    )
endif()