Don't emit ERROR here. Even GitHub Actions machines have repeated options
in /proc/cmdline.
Also see the comment in cmdline parsing for x86:
https://elixir.bootlin.com/linux/v5.16.7/source/arch/x86/boot/cmdline.c#L21
```
In accordance with standard Linux practice, if this option is repeated,
this returns the last instance on the command line.
```
name = opt
value = '' # '' is not None
if name in parsed_options:
- sys.exit(f'[!] ERROR: cmdline option "{name}" exists multiple times')
+ print(f'[!] WARNING: cmdline option "{name}" exists multiple times')
value = normalize_cmdline_options(name, value)
parsed_options[name] = value