Locally built packages are not taken into account in bob.nightlies

See: https://gitlab.idiap.ch/bob/bob.nightlies/-/jobs/162711

================================================================================
Building bob/bob.core@master (4/105)
================================================================================

...

conda.exceptions.UnsatisfiableError: The following specifications were found to be in conflict:
  - bob.blitz -> boost[version='>=1.65.1,<1.65.2.0a0'] -> libboost==1.65.1=habcd387_4
  - boost=1.67.0
Use "conda search <package> --info" to see the dependencies for each package.

while a bob.blitz package with boost 1.67 is just built in the last step.