Conditional builds skip conflicting dependencies

[AndreMiras]

In the current version of rebuild_updated_recipes.py, if two conflicting recipes got updated, the build would fail.
One way to work around it is to check it upfront and completely skip the compilation on conflicts.
Another way would be to compile deps isolated (one by one) on conflicts.
While the first way is pretty straight forward to implement, it means we won't have any coverage for conflicting recipes.