What I did to get the nightly versions.

habitat-Dockerfile.patch

diff --git a/Dockerfile b/Dockerfile
index a7b2f7d..719dbc5 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -36,6 +36,8 @@ ENV HAB_DEPOT_URL ${HAB_DEPOT_URL:-}
 RUN curl -sSf https://sh.rustup.rs \
     | env -u CARGO_HOME sh -s -- -y --no-modify-path --default-toolchain stable \
   && env -u CARGO_HOME rustup target add x86_64-unknown-linux-musl \
+  && env -u CARGO_HOME rustup install nightly \
+  && env -u CARGO_HOME rustup default nightly \
   && rustc -V \
   && cargo --version
 RUN env -u CARGO_HOME cargo install protobuf && rm -rf /root/.cargo/registry

ISSUE.md

If you are using Virtualbox and you see this:

   Compiling router v0.4.0
   Compiling habitat_depot_client v0.0.0 (file:///src/components/builder-depot-client)
   Compiling habitat_common v0.0.0 (file:///src/components/common)
error: failed to link `/src/target/debug/deps/libhabitat_director.rlib` to `/src/target/debug/libhabitat_director.rlib`

You will want to get the nightly versions of Cargo. Virtualbox does not support hardlinks as discovered in this Cargo Issue #3098.

In the nightly's, a pull-request was made to fallback to resort to plain ole cp when hardlinks does not work.