[Mingw-cross-env-list] call for testing: support for lzma archives

[Mark Brand]

 Hi,

It looks like we need to add support for unpacking .tar.lzma archives. 
The new w32api from MinGW has this format.

There are several ways to unpack these, some of which are:

tar xf foo.tar.lzma
tar xJf tar.lzma
tar -x --lzma -f foo.tar.lzma
xz -dc -F lzma foo.tar.lzma  | tar -x

It would be nice if some users could tell us which is best for your 
system, particularly if you are not using a recent version of tar. I 
wonder if we have to resort to the last method.

regards,

Mark