Consolidate Conda environment for Rust

Issue: rapidsai/build-planning#22

ci/build_rust.sh

@@ -3,15 +3,18 @@
 
 set -euo pipefail
 
+rapids-logger "Downloading artifacts from previous jobs"
+CPP_CHANNEL=$(rapids-download-conda-from-s3 cpp)
+
 rapids-logger "Create test conda environment"
 . /opt/conda/etc/profile.d/conda.sh
 
-RAPIDS_VERSION="$(rapids-version)"
-
 rapids-dependency-file-generator \
   --output conda \
   --file-key rust \
-  --matrix "cuda=${RAPIDS_CUDA_VERSION%.*};arch=$(arch);py=${RAPIDS_PY_VERSION}" | tee env.yaml
+  --matrix "cuda=${RAPIDS_CUDA_VERSION%.*};arch=$(arch);py=${RAPIDS_PY_VERSION}" \
+  --prepend-channel "${CPP_CHANNEL}" \
+  | tee env.yaml
 
 rapids-mamba-retry env create --yes -f env.yaml -n rust
 
@@ -29,13 +32,4 @@ LIBCLANG_PATH=$(dirname "$(find /opt/conda -name libclang.so | head -n 1)")
 export LIBCLANG_PATH
 echo "LIBCLANG_PATH=$LIBCLANG_PATH"
 
-rapids-logger "Downloading artifacts from previous jobs"
-CPP_CHANNEL=$(rapids-download-conda-from-s3 cpp)
-
-# installing libcuvs/libraft will speed up the rust build substantially
-rapids-mamba-retry install \
-  --channel "${CPP_CHANNEL}" \
-  "libcuvs=${RAPIDS_VERSION}" \
-  "libraft=${RAPIDS_VERSION}"
-
 bash ./build.sh rust

dependencies.yaml

@@ -89,6 +89,8 @@ files:
       - cuda_version
       - rapids_build
       - rust
+      - depends_on_libcuvs
+      - depends_on_libraft
   go:
     output: none
     includes: