CI: Use lockfile for uhyve installation

Author: stlankes

.gitlab-ci.yml

@@ -71,7 +71,7 @@ test:uhyve:
    script:
      - lscpu
      - kvm-ok
-     - cargo install uhyve
+     - cargo install uhyve --locked
      - uhyve -v -c 1 target/x86_64-unknown-hermit/debug/rusty_demo
      - uhyve -v -c 2 target/x86_64-unknown-hermit/debug/rusty_demo
      - uhyve -v -c 1 target/x86_64-unknown-hermit/release/rusty_demo