[m-rev.] diff: Fix error creating temporary archive with --restricted-command-line.

[Sebastian Godelet]

Hi Peter,

Does this also fix the problem raised here?
http://lists.mercurylang.org/archives/developers/2016-May/016574.html 
And here from the user mailing list?
http://lists.mercurylang.org/archives/users/2016-August/008192.html 
Is that the same bug, or a similar problem?

Thanks,

Sebastian.