[FEATURE] ability to add custom arguments to cli

[fariouche]

What kind of issue is this?

• Feature Request.
  Sometimes I want to create a target rule that can have an argument from the command line (like specify a key file etc)

Expected Results

Something like add_argument("--sign_key") and have it parsed using either the scons argument variable or a dedicated api

[ivankravets]

A temporary solution https://docs.platformio.org/en/latest/scripting/examples/platformio_ini_custom_options.html

[fariouche]

yes, but this one is not in command line.
I'm now using the -a option multiple times to pass arguments as a workaround