Try removing the old conda-build's build environment
Try removing the old conda-build's build environment

Old versions of `conda-build` use `_build` as the build environment.
This change attempts to remove them, but suppress the failure caused by
newer versions of `conda` if the environment cannot be removed (e.g. it
does not exist).

nanshe-org/docker_nanshe_workflow,DudLab/docker_nanshe_workflow,nanshe-org/docker_nanshe_workflow,DudLab/docker_nanshe_workflow