app/test: support resources archived by tar

app/test: support resources archived by tar

When a more complex resource (a file hierarchy) is needed, packing
every single file as a single resource would be very ineffective. For
that purpose, it is possible to pack the files into a tar archive,
extract it before test from the resource and finally clean up all the
created files.

This patch introduces functions resource_untar and resource_rm_by_tar
to perform those tasks. An example of using those functions is included
as a test.

A new dependency is required to build the app/test: libarchive.

Signed-off-by: Jan Viktorin <viktorin@rehivetech.com>