cpack installation create empty archive

[ClausKlein]

try this example project:

cmake_minimum_required(VERSION 3.28...3.30)

set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

project(cJSON-test VERSION 0.1.0 LANGUAGES CXX)

add_compile_options(-std=c17)
set(CMAKE_C_STANDARD 17)
set(CMAKE_C_EXTENSIONS NO)
set(CMAKE_C_STANDARD_REQUIRED YES)
set(CMAKE_BUILD_TYPE Release)

set(CMAKE_INSTALL_PREFIX ${CMAKE_SOURCE_DIR}/stagedir)

enable_testing()

include(FetchContent)

FetchContent_Declare(
  cJSON
  GIT_REPOSITORY https://github.com/DaveGamble/cJSON.git
  GI_TAG "v1.7.18"
  SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/cJSON-src"
  GIT_SHALLOW TRUE
)

set(ENABLE_CUSTOM_COMPILER_FLAGS OFF)
set(BUILD_SHARED_AND_STATIC_LIBS ON)

FetchContent_MakeAvailable(cJSON)

set(CPACK_GENERATOR TGZ)
include(cpack)