Change target location

Former-commit-id: 3e46e7c4dc9a66283ac5077c2db43d5eb98ae9f3

.gitlab-ci.yml

@@ -21,9 +21,8 @@ rust-nightly:
   script:
     - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain nightly
     - source /root/.cargo/env
-    - cargo build
+    - cargo build --target-dir="/cache"
     - cargo test --verbose
-    - cp target/ /cache
   allow_failure: false
 
 # # our own git fetch command like https://gitlab.com/gitlab-org/gitlab-runner/blob/master/shells/abstract.go