Fix: Quote Python path to handle spaces in postinstall scripts

[alex-lisi]

Description

Fixes installation failure when Python is installed in a directory containing spaces (e.g., C:\Program Files\Python37\).

Changes

• Modified call_pkg_script() in platformio/package/manager/base.py to wrap the Python executable path in quotes when it contains spaces
• Added isinstance(cmd, list) check before accessing list elements (addresses feedback from Fix: Quote Python path to handle spaces in postinstall scripts #5363)
• This prevents the shell from incorrectly splitting the path during postinstall script execution

Testing

• Fix follows same pattern as Fix: Quote cc_path to handle spaces in microcontroller names #5351 (spaces in microcontroller names)
• Handles both list and string command formats

Related Issue

Fixes #5361

Notes

This is a revised version of #5363 incorporating maintainer feedback.