gitlab ci improvements: cache target & .cargo, separate test and build

.gitlab-ci.yml

@@ -1,5 +1,13 @@
 image: "rust:latest"
 
+variables:
+  CARGO_HOME: $CI_PROJECT_DIR/.cargo
+
+cache:
+  paths:
+    - target
+    - .cargo
+
 default:
   before_script:
     - rustc --version 
@@ -12,7 +20,6 @@ build:
   stage: build
   script:
     - cargo build --verbose
-    - cargo test --verbose
 
 cargo-test:
   stage: test