Fix

Author: tstellar

.github/workflows/premerge.yaml

@@ -36,6 +36,12 @@ jobs:
     runs-on: ${{ matrix.runs-on }}
     container:
       image: ${{ (startsWith(matrix.runs-on, 'ubuntu-24.04') && format('ghcr.io/{0}/ci-ubuntu-24.04',github.repository_owner) ) || null }}
+    defaults:
+      run:
+        # The run step defaults to using sh as the shell when running in a
+        # container, so make bash the default to ensure consistency between
+        # container and non-container jobs.
+        shell: bash
     steps:
       - name: Checkout LLVM
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0