Update gradle and improve realiablitity of actions (#1804)

* improve github actions

* fix

* update gradle and fix

.github/workflows/build.yml

@@ -4,15 +4,12 @@ jobs:
   build:
     strategy:
       matrix:
-        java-version: [1.8, 11, 14]
+        java: [8-jdk, 11-jdk, 14-jdk]
     runs-on: ubuntu-20.04
+    container:
+      image: openjdk:${{ matrix.java }}
+      options: --user root
     steps:
       - uses: actions/checkout@v1
       - uses: gradle/wrapper-validation-action@v1
-      - uses: actions/setup-java@v1
-        with:
-          java-version: ${{ matrix.java-version }}
-      - uses: eskatos/gradle-command-action@v1.3.2
-        with:
-          gradle-version: wrapper
-          arguments: build javadocJar checkMappings --stacktrace
+      - run: ./gradlew build javadocJar checkMappings --stacktrace

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.3-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.6.1-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists