CI: only build debian-contrib when contribs/tools/CI change
For now we don't use the result. It doesn't really matter if the contribs with our patches build on Linux.
The debian-contrib build is even blocking MR's that don't even need to build the contribs: !4148 (merged) It's also failing a lot of MR's that don't need to build contribs either: !4202 (merged), !4206 (merged) !4210 (merged)
Edited by Steve Lhomme