ci: enable arm64 runner for build/unit jobs

Enable only a couple of jobs, to avoid running down capacity too much

.github/workflows/unit_tests.yml

@@ -14,17 +14,22 @@ permissions:
 
 jobs:
   build:
-    runs-on: ubuntu-24.04
+    runs-on: ${{ matrix.runner }}
     concurrency:
-      group: ${{ github.workflow }}-${{ matrix.run_phase }}-${{ github.ref }}
+      group: ${{ github.workflow }}-${{ matrix.run_phase }}-${{ github.ref }}-${{ matrix.runner }}
       cancel-in-progress: true
     strategy:
       fail-fast: false
       matrix:
+        runner: [ ubuntu-24.04 ]
         run_phase: [GCC, GCC_ASAN_UBSAN, CLANG, CLANG_RELEASE, CLANG_ASAN_UBSAN, CLANG_ASAN_UBSAN_NO_DEPS]
         include:
           - run_phase: GCC
+          - run_phase: GCC
+            runner: ubuntu-24.04-arm
           - run_phase: CLANG
+          - run_phase: CLANG
+            runner: ubuntu-24.04-arm
     steps:
       - name: Repository checkout
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683