ci: ensure the registry cache and lockfile are up-to-date

We are caching the CARGO_HOME which includes git repos of
the gtk-rs bindings. Since we don't specify a branch
so it uses the default branch for the ref.

cargo build usually does an update if it has network access,
but its not guaranteed or the case for other tools like clippy
which may still point to the stale git snapshot like here:

https://gitlab.freedesktop.org/thaytan/gstreamer-rs/-/jobs/4165449

.gitlab-ci.yml

@@ -16,6 +16,12 @@ stages:
   before_script:
     - source ./ci/env.sh
     - mkdir .cargo && echo -e "[net]\ngit-fetch-with-cli = true" > .cargo/config
+    # If cargo exists assume we probably will want to update the lockfile
+    - |
+      if command -v cargo; then
+        cargo generate-lockfile
+        cargo update
+      fi
   cache:
     key: "gst"
     paths:
@@ -41,14 +47,14 @@ stages:
   script:
     - rustc --version
     - cargo --version
-    - cargo build --all --color=always
+    - cargo build --locked --all --color=always
     # FIXME: tests are broken
     # https://github.com/sdroege/gstreamer-sys/issues/16
-    # - cargo test --all --color=always
+    # - cargo test --locked --all --color=always
-    - cargo build --all --all-features --color=always
+    - cargo build --locked --all --all-features --color=always
     # FIXME: tests are broken
     # https://github.com/sdroege/gstreamer-sys/issues/16
-    # - cargo test --all --all-features --color=always
+    # - cargo test --locked --all --all-features --color=always
 
     # Run tests for crates we can currently run. The others
     # need a new release of the C library first
@@ -69,7 +75,7 @@ stages:
                      gstreamer-video-sys \
                      gstreamer-webrtc-sys; \
             do \
-                cargo test -p $crate; \
+                cargo test --locked -p $crate; \
             done
 
 test stable: