Fix unmasking build section for noarch_python
Fix unmasking build section for noarch_python

The code was checking equality rather than assigning.

I guess no-one actually used this option?
dan-blanchard/conda-build,ilastik/conda-build,ilastik/conda-build,sandhujasmine/conda-build,sandhujasmine/conda-build,dan-blanchard/conda-build,dan-blanchard/conda-build,sandhujasmine/conda-build,ilastik/conda-build