Make argfile work (more) like javac

[som-snytt]

Reproduction steps

Scala version: 2.13.10

scalac @file expects an arg per line instead of parsing argfile lines. This breaks existing argfiles.

Instead, respect javac conventions (which appear to be similar to previous behavior):

An argument file can include command-line options and source file names in any combination. The arguments within a file can be separated by spaces or new line characters. If a file name contains embedded spaces, then put the whole file name in double quotation marks.

javac tolerates the following variant quotations:

-d "target dir"

-d "target di"r

-d "targ"et

-d "target

-d 'target dir'

The following creates the output dir target dir", and demonstrates that javac does not model fine behavior.

-d 'target dir"

Problem

Maintain compatibility with once and future versions, including WWJD.

Per the doc for javac, quotation is intended to support spaces in file paths, as opposed to shell-style command lines.

Noticed at scala/scala#10316

[som-snytt]

Make sure -Vprint-args does the compatible thing.

[lrytz]

previous behavior

Which previous behavior are you referring to?

[lrytz]

... found it; 2.13.9, according to scala/scala#10316.