mqtt: list files manually in component cmake file

components/mqtt/CMakeLists.txt

@@ -1,6 +1,10 @@
 set(COMPONENT_ADD_INCLUDEDIRS esp-mqtt/include)
 set(COMPONENT_PRIV_INCLUDEDIRS "esp-mqtt/lib/include")
-set(COMPONENT_SRCDIRS esp-mqtt esp-mqtt/lib)
+set(COMPONENT_SRCS "esp-mqtt/mqtt_client.c"
+                   "esp-mqtt/lib/mqtt_msg.c"
+                   "esp-mqtt/lib/mqtt_outbox.c"
+                   "esp-mqtt/lib/platform_esp32_idf.c"
+                   "esp-mqtt/lib/transport_ws.c")
 
 set(COMPONENT_REQUIRES lwip nghttp mbedtls tcp_transport)