Fail action execution on unhandled errors

Without this, the error logs contain an "UnhandledPromiseRejectionError"
but the action is reported as succeeding.

.github/workflows/failure-cases.yml

@@ -11,26 +11,27 @@ env:
   CACHE_KEY_PREFIX: ${{github.workflow}}#${{github.run_number}}-
 
 jobs:
+
   wrapper-missing:
+    continue-on-error: true
     runs-on: ubuntu-latest
     steps:
     - name: Checkout sources
       uses: actions/checkout@v2
     - name: Test wrapper missing
       uses: ./
-      continue-on-error: true
       with:
         build-root-directory: __tests__/samples/no-wrapper
         arguments: help
 
   bad-configuration:
+    continue-on-error: true
     runs-on: ubuntu-latest
     steps:
     - name: Checkout sources
       uses: actions/checkout@v2
     - name: Test bad config value
       uses: ./
-      continue-on-error: true
       with:
         build-root-directory: __tests__/samples/no-wrapper
         arguments: help