Add a new ENV var with the path to ROM images for IDF

Author: valeros

builder/frameworks/espidf.py

@@ -284,6 +284,8 @@ def populate_idf_env_vars(idf_env):
     if board.get("build.esp-idf.overwrite_managed_components", "yes") == "yes":
         idf_env["IDF_COMPONENT_OVERWRITE_MANAGED_COMPONENTS"] = "1"
 
+    idf_env["ESP_ROM_ELF_DIR"] = platform.get_package_dir("tool-esp-rom-elfs")
+
 
 def get_target_config(project_configs, target_index, cmake_api_reply_dir):
     target_json = project_configs.get("targets")[target_index].get("jsonFile", "")