idf_tools.py: fix virtualenv issue for macOS with homebrew

tools/idf_tools.py

@@ -1344,6 +1344,11 @@ def main(argv):
     global global_idf_tools_path
     global_idf_tools_path = os.environ.get('IDF_TOOLS_PATH') or os.path.expanduser(IDF_TOOLS_PATH_DEFAULT)
 
+    # On macOS, unset __PYVENV_LAUNCHER__ variable if it is set.
+    # Otherwise sys.executable keeps pointing to the system Python, even when a python binary from a virtualenv is invoked.
+    # See https://bugs.python.org/issue22490#msg283859.
+    os.environ.pop('__PYVENV_LAUNCER__', None)
+
     if sys.version_info.major == 2:
         try:
             global_idf_tools_path.decode('ascii')