I have a need to create tar archives deterministically
and reproducibly. Since we already have similar functionality in
mozpack for producting zip/jar archives, I figured it made sense for
this functionality to live in mozpack.
I made the functionality as simple as possible: we only accept
files from the filesystem and the set of files must be known in
advance. No class to hold/buffer state: just a simple function
that takes a mapping of files and writes to a stream.
MozReview-Commit-ID: If0NTcA7wpc
