add check for valid build/pin_depends value
add check for valid build/pin_depends value

sandhujasmine/conda-build,ilastik/conda-build,ilastik/conda-build,sandhujasmine/conda-build,dan-blanchard/conda-build,dan-blanchard/conda-build,sandhujasmine/conda-build,ilastik/conda-build,dan-blanchard/conda-build