Reset IDF_PATH environment variable

Clear the IDF_PATH environment variable.

Author: Jason2866

platform.py

@@ -98,6 +98,7 @@
 PROJECT_CORE_DIR=ProjectConfig.get_instance().get("platformio", "core_dir")
 IDF_TOOLS_PATH=os.path.join(PROJECT_CORE_DIR)
 os.environ["IDF_TOOLS_PATH"] = IDF_TOOLS_PATH
+os.environ['IDF_PATH'] = ""
 
 # Global variables
 python_exe = get_pythonexe_path()