Fix cabal run's handling of -- under empty target

[ulysses4ever]

fix #10487, created with the help from AI (GitHub Copilot).

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[ulysses4ever]

i removed the commit touching up the Makefile doctest setup since this issue has been attended to elsewhere

[ulysses4ever]

Apparently some of the new tests were incorrect @philderbeast

[philderbeast]

Apparently some of the new tests were incorrect @philderbeast

The review comment substitution didn't work. It didn't delete lines 3 .. 16 (in what I'm seeing now with cb107bb) that I'd included in the selection for replacement.

I think you may also need a type annotation for the opts:

+ opts1, opts2, opts3 :: [String]
  opts1 = ["+RTS"]
  opts2 = ["+RTS", "--"]
  opts3 = ["--", "+RTS"]

You'll also need to run the test with --accept to generate cabal-testsuite/PackageTests/NewBuild/CmdRun/WarningRTS/cabal.no-target.out.

[ulysses4ever]

Thanks, will fix. Also: those opts make tests harder to read imo, so I plan to inline them.