Run x86_64-gnu in PR tests

Author: Zalathar

.github/workflows/ci.yml

@@ -62,6 +62,10 @@ jobs:
             tidy: false
             os: ubuntu-20.04-16core-64gb
             env: {}
+          - name: x86_64-gnu
+            tidy: false
+            os: ubuntu-20.04-8core-32gb
+            env: {}
     timeout-minutes: 600
     runs-on: "${{ matrix.os }}"
     steps:

src/ci/github-actions/ci.yml

@@ -320,6 +320,10 @@ jobs:
             <<: *job-linux-16c
             tidy: false
 
+          - name: x86_64-gnu
+            <<: *job-linux-8c
+            tidy: false
+
   auto:
     permissions:
       actions: write # for rust-lang/simpleinfra/github-actions/cancel-outdated-builds