Install idoc in the Fedora CI container

This gives us access to both idoc and the necessary dependencies to
build the compiler from source. This in turn is needed so we can
document code (e.g. new intrinsics) that requires features not available
in the latest stable release.

.github/workflows/containers.yml

@@ -25,7 +25,3 @@ jobs:
     uses: ./.github/workflows/container.yml
     with:
       name: 'ubuntu'
-  idoc:
-    uses: ./.github/workflows/container.yml
-    with:
-      name: 'idoc'

ci/docker/fedora/Dockerfile

@@ -15,3 +15,9 @@ RUN sudo dnf install --assumeyes --quiet gcc make tar git rustup rclone \
 
 RUN rustup-init --quiet -y --no-modify-path --profile minimal \
     --component clippy,rustfmt --default-toolchain $RUST_VERSION
+
+# idoc targets the latest stable release of Inko, but our tests run against a
+# newer version. This allows us to use an existing idoc executable without
+# having to compile it ourselves.
+COPY --from=ghcr.io/inko-lang/idoc:latest ["/usr/bin/idoc", "/usr/bin/idoc"]
+COPY --from=ghcr.io/inko-lang/idoc:latest ["/usr/share/idoc/assets", "/usr/share/idoc/assets"]