Fix Issue 22575 - putting -run in dmd.conf causes a segfault

[Wesley-Jenkins]

Length in "-run" code only considers command line args, causing an underflow here. This fixes the segfault, but breaks everything else, because it eats the rest of the arguments, and then it can't compile. So I'm not sure if it's easily possible to allow "-run" in a dmd.conf file, and maybe it should just error upon encountering it.

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[rainers]

Tests fail because options from DFLAGS are appended to the command line arguments and are now ignored for compilation. As you suggested, maybe it's just better to bail out if -run is inside a response file or environment variable, which might be possible to check via i >= argc.

[RazvanN7]

@Wesley-Jenkins are you still pursuing this?

[dkorpel]

Ping @Wesley-Jenkins

[ljmf00]

This needs the issue number reference in the commit.