fix(ci): Conformance test: Abort on failure in any command in the run section

By default, all commands in the `run` section of
`.github/workflows/conformance.yml` are executed, regardless of their
return values and the return value of the last command is used as the
result for the entire flow. Failing test followed by passing tests
thus remain undetected.

This change forces the use of the bash shell and causes it to exit
immediately with a non-zero return value when one of the commands
fails using `set -e`.

.github/workflows/conformance.yml

@@ -30,7 +30,9 @@ jobs:
           username: ${{ secrets.GHCR_LOGIN }}
           password: ${{ secrets.GHCR_PASSWORD }}
           options: -v ${{ github.workspace }}/compiler:/compiler
+          shell: bash
           run: |
+            set -e
             echo "Debug: ccache statistics (prior to the build):"
             ccache -s
             cd /compiler