feat(mqtt): Stop cmake process if submodule is missing

Closes https://github.com/espressif/esp-idf/issues/12202

components/mqtt/CMakeLists.txt

@@ -1 +1,6 @@
-include(${CMAKE_CURRENT_LIST_DIR}/esp-mqtt/CMakeLists.txt)
+if(NOT EXISTS ${CMAKE_CURRENT_LIST_DIR}/esp-mqtt/CMakeLists.txt)
+    set(COMMAND  "git submodule update --init --recursive")
+    message(FATAL_ERROR "Missing esp-mqtt submodule. Please run '${COMMAND}' in ESP-IDF directory to fix this.")
+else()
+    include(${CMAKE_CURRENT_LIST_DIR}/esp-mqtt/CMakeLists.txt)
+endif()