ci: enable build/unit test jobs on ppc64le

New workers we got from IBM can be used now. The GHA linter doesn't
recognize them yet, so add a local workaround until the change is
merged in the linter.

.github/linters/actionlint.yml

@@ -0,0 +1,6 @@
+self-hosted-runner:
+  # Linter only knows Github's runners, these are from IBM
+  labels:
+    - ubuntu-24.04-ppc64le
+    - ubuntu-24.04-ppc64le-p10
+    - ubuntu-24.04-s390x

.github/workflows/build_test.yml

@@ -32,6 +32,8 @@ jobs:
           - { COMPILER: "clang", COMPILER_VERSION: "16", LINKER: "bfd"  }
           - { COMPILER: "clang", COMPILER_VERSION: "18", LINKER: "lld"  }
         include:
+          - env: { COMPILER: "gcc",   COMPILER_VERSION: "11", LINKER: "bfd"  }
+            runner: [ ubuntu-24.04-ppc64le ]
           - env: { COMPILER: "gcc",   COMPILER_VERSION: "13", LINKER: "mold"  }
             runner: [ ubuntu-24.04-arm ]
     env: ${{ matrix.env }}

.github/workflows/linter.yml

@@ -35,6 +35,8 @@ jobs:
           MULTI_STATUS: false
           VALIDATE_ALL_CODEBASE: false
           VALIDATE_GITHUB_ACTIONS: true
+          LINTER_RULES_PATH: .github/linters
+          GITHUB_ACTIONS_CONFIG_FILE: actionlint.yml
 
       - uses: systemd/mkosi@0d1143150835b21c1bfe64428df5f45b558280b1
 

.github/workflows/unit_tests.yml

@@ -27,9 +27,13 @@ jobs:
           - run_phase: GCC
           - run_phase: GCC
             runner: ubuntu-24.04-arm
+          - run_phase: GCC
+            runner: ubuntu-24.04-ppc64le
           - run_phase: CLANG
           - run_phase: CLANG
             runner: ubuntu-24.04-arm
+          - run_phase: CLANG
+            runner: ubuntu-24.04-ppc64le
     steps:
       - name: Repository checkout
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683