Make it possible to output verbatim cmd arguments

[nkaretnikov]

Spent quite a while yesterday trying to understand why gcc didn't like my linker script, resulting in a generic error, while the printed command in the output worked fine. I suspected formatting issues early enough, but still some time was spent searching for the said generic error on the web. Turned out I needed to pass my ldflags as a string rather than a list of strings, so a single unwords did it.

I know there's a note about that in the haddocks. Still, it would be nice to dump something unambiguous. Show output, perhaps, if it's just value constructors, assuming it's not too verbose (haven't looked at the relevant instances, maybe it's worthless).

[nkaretnikov]

(In addition to the existing output, of course.)

[ndmitchell]

What about the current printing sufficient? I would expect it to differ between:

link "-La b c"
link -La b c

Can you give an example of the output you got from the command failure? And what that corresponded to underneath? The Show output captures a lot of internal details to Shake, but in the end it's either a String (for Shell) or [String]. However, I had hoped the existing show was unambiguous enough - if not, I'd like to do better.

[ndmitchell]

Closing since I don't have an example to work with (please reopen if you can give the example - I'm keen to fix it if I can reproduce).