mamba fails to resolve osx-arm64 build environment in conda-forge CI only

[duncanmmacleod]

Mamba (via conda mambabuild) is failing to resolve the host environment for a build, but only when running as part of the conda-forge azure CI for a feedstock build:

Mamba failed to solve:
 - gsl 2.7.*
 - fftw * nompi*
 - liblal
 - liblalframe
 - liblalinference
 - liblalsimulation

with channels:

The reported errors are:
- Encountered problems while solving:
-   - package liblalframe-1.5.5-h3422bc3_0 requires ldas-tools-framecpp >=2.7.2,<2.8.0a0, but none of the providers can be installed
- 

I cannot reproduce this on any other machine, but it seems reliable on conda-forge CI. conda build has no trouble with this particular build. I have seen the same error across a number of (related) feedstocks, so I think don't think anything here is feedstock specific.