Currently the recipes use absolute paths, try to fix it with use of relative paths instead

[jimklimov]

Envs:

• builds in Travis
• builds in Jenkins (e.g. can not cleanup after stages and use different agents in parallel, because unstashed code for test dirs requires presence of original build dirs and contents)
• builds in FTY repo (locally and Travised)

Problems:

• ecpp generates .cc files into original srcdir, not into clone (FTY repo)
• Jenkins cleanup impacted
• (not proven) can possibly be an issue for OBS builds using Jenkins-provided tarballs with docs etc., if there are some other files that are generated with such paths...