Skip the 'download-dist' step for full integ-test

After the '[bot] update dist directory' commit, we run a full test suite.
This will now use the content from the 'dist' directory, rather than
regenerating this content in the test.

.github/workflows/integ-test-sample-gradle-plugin.yml

@@ -8,8 +8,12 @@ on:
       runner-os:
         type: string
         default: '["ubuntu-latest", "windows-latest", "macos-latest"]'
+      skip-dist:
+        type: boolean
+        default: false
 
 env:
+  SKIP_DIST: ${{ inputs.skip-dist }}
   GRADLE_BUILD_ACTION_CACHE_KEY_PREFIX: sample-gradle-plugin-${{ inputs.cache-key-prefix }}
 
 jobs: