Set CONDA_DEFAULT_ENV in the build environment
Set CONDA_DEFAULT_ENV in the build environment

This lets you run conda commands in the build script (which is necessary,
e.g., to remove setuptools).

frol/conda-build,sandhujasmine/conda-build,shastings517/conda-build,mwcraig/conda-build,frol/conda-build,rmcgibbo/conda-build,ilastik/conda-build,rmcgibbo/conda-build,rmcgibbo/conda-build,sandhujasmine/conda-build,sandhujasmine/conda-build,shastings517/conda-build,frol/conda-build,mwcraig/conda-build,dan-blanchard/conda-build,dan-blanchard/conda-build,dan-blanchard/conda-build,ilastik/conda-build,ilastik/conda-build,shastings517/conda-build,mwcraig/conda-build