Mention chroot in --batch description.
Mention chroot in --batch description.

Fixes #134.

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MOS_MIGRATED_REVID=103935102

bazelbuild/bazel-website,davidzchen/bazel-website,bazelbuild/bazel-website,bazelbuild/bazel-website,davidzchen/bazel-website,davidzchen/bazel-website,davidzchen/bazel-website