Build PR with Java 8

Issue gh-761

.github/workflows/pr-build-workflow.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest]
-        jdk: [11]
+        jdk: [8]
       fail-fast: false
     steps:
       - uses: actions/checkout@v2