Use Java8

.gitlab-ci.yml

@@ -14,13 +14,13 @@ cache:
     - .gradle/caches
 
 build:
-  image: openjdk:11
+  image: openjdk:8
   stage: build
   script:
     - ./gradlew assemble
 
 createDoc:
-  image: openjdk:11
+  image: openjdk:8
   stage: build
   script:
     - "./gradlew :run"
@@ -29,7 +29,7 @@ createDoc:
       - "pages/docs/config.md"
 
 publish:
-  image: openjdk:11
+  image: openjdk:8
   stage: publish
   script:
     - "./gradlew setDevVersionForCI"

build.gradle

@@ -16,6 +16,8 @@ gradlePlugin {
     }
 }
 
+java.toolchain.languageVersion = JavaLanguageVersion.of(8)
+
 def versionFile = 'src/main/resources/PreprocessorTesting.properties'
 def oldProps = new Properties()