build := exec.Command("singularity", "build", imageFilename, "docker-archive://"+e.tmpdir+"/image.tar")
build.Env = os.Environ()
build.Env = append(build.Env, "SINGULARITY_CACHEDIR="+e.tmpdir+"/cache")
build := exec.Command("singularity", "build", imageFilename, "docker-archive://"+e.tmpdir+"/image.tar")
build.Env = os.Environ()
build.Env = append(build.Env, "SINGULARITY_CACHEDIR="+e.tmpdir+"/cache")