Private builds have broken links

The links to the build result, logs and reports of private Offspring builds are all broken because they point to the standard path under snapshots.linaro.org, but private builds are obviously not synced there as that's public.

In order to fix this we need to define a standard place to where private builds are synced. Currently we use snapshots.l.o/hwpacks/<lt-name> and maybe that's good enough.