It doesn't make much sense to package piglit or install on machines, due
to the frequency piglit tests are added/changed.

However, binary packages are still useful for distributed testing where
the binaries are built on one machine, and then passed to (sometimes
other teams) for the actual testing.

This patch allows one to conveniently generate such packages, simply by
doing

  make package

Then one can run piglit by unpacking the package elsewhere, set the
PIGLIT_SOURCE_DIR and LD_LIBRARY_PATH accordingly, and run piglit scripts
as usual.

Reviewed-by: Brian Paul <brianp@vmware.com>