CI: enable example builds for C3

Enables building C3 examples in CI.

Fixes related warnings/errors and disables examples that cannot run.


* Original commit: espressif/esp-idf@04df1f3a42

components/freemodbus/CMakeLists.txt

@@ -1,7 +1,4 @@
 idf_build_get_property(target IDF_TARGET)
-if(${target} STREQUAL "esp32c3")
-            return()  # TODO ESP32-C3 IDF-2173
-endif()
 
 # The following five lines of boilerplate have to be in your project's
 # CMakeLists in this exact order for cmake to work correctly

components/freemodbus/port/port.h

@@ -17,7 +17,6 @@
 #define PORT_COMMON_H_
 
 #include "freertos/FreeRTOS.h"
-#include "freertos/xtensa_api.h"
 #include "esp_log.h"                // for ESP_LOGE macro
 #include "mbconfig.h"