check polkadot for companion pull requests (#5262)

* check_polkadot: move to external script

* check_polkadot: check for companion pr

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/.gitlab-ci.yml

@@ -127,6 +127,15 @@ check-line-width:
   allow_failure:                   true
 
 
+check-polkadot:
+  stage:                           build
+  <<:                              *docker-env
+  script:
+    - ./.maintain/gitlab/check_polkadot.sh
+  interruptible:                   true
+  allow_failure:                   true
+
+
 cargo-audit:
   stage:                           test
   <<:                              *docker-env
@@ -410,30 +419,6 @@ check_warnings:
         echo "___No warnings___";
       fi
 
-# Nightly check whether Polkadot 'master' branch builds.
-check_polkadot:
-  stage:                           build
-  <<:                              *docker-env
-  allow_failure:                   true
-  only:
-    - master
-    - schedules
-  script:
-    - SUBSTRATE_PATH=$(pwd)
-    # Clone the current Polkadot master branch into ./polkadot.
-    - git clone --depth 1 https://gitlab.parity.io/parity/polkadot.git
-    - cd polkadot
-    # Make sure we override the crates in native and wasm build
-    - mkdir .cargo
-    - echo "paths = [ \"$SUBSTRATE_PATH\" ]" > .cargo/config
-    - mkdir -p target/debug/wbuild/.cargo
-    - echo "paths = [ \"$SUBSTRATE_PATH\" ]" > target/debug/wbuild/.cargo/config
-    # package, others are updated along the way.
-    - cargo update
-    # Check whether Polkadot 'master' branch builds with this Substrate commit.
-    - time cargo check
-    - cd -
-    - sccache -s
 
 trigger-contracts-ci:
   stage:                           publish