[CI] Fix release notification message, and add rustc version to release notes (#1191)

* Release announcements: s/kusama/polkadot/

* Additional debug info for gitlab publish script

* add rustc version check job

* fully comment out tag-checking

* s/podman/docker/g

* Switch to rust-builder image and install jq

* remove temporary TODOs

polkadot/scripts/gitlab/publish_draft_release.sh

@@ -24,9 +24,13 @@ case $? in
     ;;
   1) echo '[!] Tag found but has not been signed. Aborting release.'; exit 1
     ;;
-  2) echo '[!] Tag not found. Aborting release.'; exit
+  2) echo '[!] Tag not found. Aborting release.'; exit 1
 esac
 
+# Pull rustc version used by rust-builder for stable and nightly
+stable_rustc="$(rustc +stable --version)"
+nightly_rustc="$(rustc +nightly --version)"
+
 # Start with referencing current native runtime
 # and find any referenced PRs since last release
 # Note: Drop any changes that begin with '[contracts]' or 'contracts:'
@@ -41,6 +45,10 @@ release_text="Polkadot native runtime: $polkadot_spec
 Kusama native runtime: $kusama_spec
 
 Westend native runtime: $westend_spec
+
+This release was built with the following versions of \`rustc\`. Other versions may work.
+- $stable_rustc
+- $nightly_rustc
 "
 
 runtime_changes=""