pyside6-deploy: Use "shlex.split(extra_args)" instead of "extra_args.split()" in nuitka_helper.py

In pysidedeploy.spec, if any of the arguments of extra_args contains a space, Nuitka will throw an error even if that argument is surrounded by quotes.

For example:

extra_args = ... --macos-app-name="App Name"

will throw an error:

FATAL: 
Error, specify only one positional argument unless "--run" is specified to
pass them to the compiled program execution.

as it is trying to naively split the arguments by space:

subprocess.CalledProcessError: Command '[..., '--macos-app-name="App', 'Name"', ...]' returned non-zero exit status 1.

This can be fixed by replacing

extra_args = extra_args.split()

with

import shlex
extra_args = shlex.split(extra_args)

This will correctly parse the argument string and split it as if it were a real command entered on the command line, preserving quoted strings and spaces escaped with a backslash.