Also try to cache $CARGO_HOME

.gitlab-ci.yml

@@ -3,12 +3,15 @@ image: "rust:latest"
 cache:
   paths:
     - target
+    - cargohome
 
 
 variables:
   GIT_SUBMODULE_STRATEGY: recursive
+  CARGO_HOME: "CI_PROJECT_DIR/cargohome"
 
 before_script:
+  - mkdir -p $CARGO_HOME && echo "using $CARGO_HOME to cache cargo deps"
   - apt-get update -yqq
   - apt-get install -yqq --no-install-recommends build-essential libssl-dev pkg-config
   - rustup component add clippy rustfmt