Restore -Vprint-args, for echoing arguments provided to compiler

[som-snytt]

It was accidentally put back on the info arg list. Insult to injury, its "-" arg was no longer parsed.

Unreverts and improves #10123

Note that this is irrespective of how "command lines" are tokenized, as arg files are no longer tokenized.

Apologies to retronym, who set up the current facility in 2018, which I broke in 2019 (but only on 2.13, which must be why retronym didn't notice).

[som-snytt]

The default for -Vprint-args is "-", which means that the user setting -Vprint-args - does not show up in the resulting output, ironically. The default should be empty string; feature is triggered by value set by user. Changing it is left to future generations, so that they cannot say that we left nothing for them to do.