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

@@ -27,6 +27,13 @@ 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
 
 .debian:10-stable:
   extends: .debian:10
@@ -121,10 +128,11 @@ update-nightly:
   stage: "test"
   script:
     - rustc --version
-    - cargo build --color=always --all
-    - G_DEBUG=fatal_warnings cargo test --color=always --all
-    - cargo build --color=always --all --examples --all-features
-    - G_DEBUG=fatal_warnings cargo test --color=always --all --examples --all-features
+
+    - cargo build --locked --color=always --all
+    - G_DEBUG=fatal_warnings cargo test --locked --color=always --all
+    - cargo build --locked --color=always --all --examples --all-features
+    - G_DEBUG=fatal_warnings cargo test --locked --color=always --all --examples --all-features
 
 test 1.40:
   extends:
@@ -171,7 +179,7 @@ clippy:
   rules:
     - when: 'always'
   script:
-    - cargo clippy --color=always --all --all-features --all-targets -- -A clippy::redundant_pattern_matching -A clippy::single_match -A clippy::cast_lossless -D warnings
+    - cargo clippy --locked --color=always --all --all-features --all-targets -- -A clippy::redundant_pattern_matching -A clippy::single_match -A clippy::cast_lossless -D warnings
 
 deny:
   extends: .img-stable