add libarchive tar files

[danmoseley]

tracking adding libarchive tar files, if we get an OK in libarchive/libarchive#1767

cc @carlossanlop

[danmoseley]

Our questions were answered.

[danmoseley]

@am11 FYI in case you want to look at this. In the issue, they noted that their tests that construct tar files on the fly might be more interesting. But we can at least add and consume the tar files they do have.