remove folder if exist

CMake/json-download.cmake.in

@@ -9,13 +9,17 @@ ExternalProject_Add(
     # We do not use 'GIT_REPOSITORY' as it doesn't support a shallow clone of a specific commit,
     # this make the clone step very long, so we clone by ourselves (See https://gitlab.kitware.com/cmake/cmake/-/issues/17770).
     # Adding detachedHead=false to avoid warnings like: "You are in 'detached HEAD' state..."
-    DOWNLOAD_COMMAND   git clone -c advice.detachedHead=false --branch v3.11.3 https://github.com/nlohmann/json.git --depth 1 json
-    DOWNLOAD_DIR       "${CMAKE_BINARY_DIR}/third-party/"
+    # 'remove_directory' is working but cound as deprecated from cmake version 3.17, 
+    # Once we have a minimal version support of cmake 3.17, we can switch the command to rm -rF
+    DOWNLOAD_COMMAND   "${CMAKE_COMMAND}" -E  remove_directory  "${CMAKE_BINARY_DIR}/third-party/json"
+             COMMAND   git clone -c advice.detachedHead=false --branch v3.11.3 https://github.com/nlohmann/json.git --depth 1 json
+    DOWNLOAD_DIR       ${CMAKE_BINARY_DIR}/third-party/
 
     # Override default steps with no action, we just want the clone step.
     UPDATE_COMMAND ""
     CONFIGURE_COMMAND ""
     BUILD_COMMAND ""
     INSTALL_COMMAND ""
     )
-
+
+