ci: Install rustdoc-stripper in Nightly Rust image

This saves two build-jobs from performing the same (expensive!)
compilation+installation over and over again, when it is much cheaper to
cache it in the image instead.

.gitlab-ci.yml

@@ -1,7 +1,7 @@
 # We use https://gitlab.freedesktop.org/freedesktop/ci-templates
 # to build the images used by the ci.
 #
-# Here is how to properly update thoses images:
+# Here is how to properly update those images:
 # - new Rust stable version: update GST_RS_IMG_TAG and update Rust version
 # - add dependencies: update FDO_DISTRIBUTION_PACKAGES and update GST_RS_IMG_TAG
 # - update GStreamer version: update the tag in ci/install-gst.sh and update GST_RS_IMG_TAG
@@ -11,7 +11,7 @@
 # - setting it to the current date and the version suffix to 0
 # - incrementing the version suffix
 #
-# After each update commit your changes and push to your personnal repo.
+# After each update commit your changes and push to your personal repo.
 # After review and ci approval merge the branch as usual.
 #
 # Updating the nightly image should be done by simply running a scheduled ci
@@ -450,7 +450,6 @@ doc-stripping:
   extends: .img-nightly
   stage: 'extras'
   script:
-    - cargo install rustdoc-stripper
     - PATH=~/.cargo/bin/:$PATH ./generator.py --strip-docs --no-fmt
     - git diff --quiet || (echo 'Files changed after running `rustdoc-stripper -s`, make sure all documentation is protected with `// rustdoc-stripper-ignore-next`!'; git diff; false)
 
@@ -460,7 +459,6 @@ docs:
   extends: .img-nightly
   stage: 'extras'
   script:
-    - cargo install rustdoc-stripper
     - PATH=~/.cargo/bin/:$PATH ./generator.py --embed-docs --no-fmt
     - |
       crate_names=$(for manifest in gstreamer*/Cargo.toml; do echo -n " -p ${manifest%%/Cargo.toml}"; done)

ci/images_template.yml

@@ -1,4 +1,4 @@
 variables:
-  GST_RS_IMG_TAG: '2021-04-23.1'
+  GST_RS_IMG_TAG: '2021-05-05.0'
   GST_RS_STABLE: '1.51.0'
   GST_RS_MSRV: '1.51.0'

ci/install-rust.sh

@@ -27,8 +27,11 @@ if [ "$RUST_IMAGE_FULL" = "1" ]; then
   cargo install --force cargo-outdated
 fi
 
-# coverage tools
 if [ "$RUST_VERSION" = "nightly" ]; then
+  # Coverage tools
   cargo install grcov
   rustup component add llvm-tools-preview
+
+  # Documentation tools
+  cargo install --force rustdoc-stripper
 fi