ghw-snapshot: use relative links for block devs
ghw-snapshot: use relative links for block devs

When snapshotting the block device tree structure,
better use relative paths - not absolute, otherwise
the link target will reference the buildDir path (not
the unpackDir path), making the link broken.

Signed-off-by: Francesco Romani <c7100b580e6017ef67482ace46578cdd2d2e0dfe@redhat.com>

jaypipes/ghw,jaypipes/ghw