Reactivated travis build with openjdk 15

.gitignore

@@ -1,7 +1,6 @@
 .gradle
 .idea
 *.iml
-gradlew
 gradlew.bat
 gradle.properties
 gradle

.travis.yml

@@ -1,11 +1,10 @@
 language: java
+dist: trusty
 jdk:
   - oraclejdk8
 
 before_install:
   - gradle wrapper
-  - chmod +x scripts/run-xvfb
-  - scripts/run-xvfb
 install: true
 
 addons:
@@ -14,4 +13,13 @@ addons:
   ssh_known_hosts: onaple.fr
 
 script:
-  - ./gradlew sonarqube --stacktrace -x test
+  - ./gradlew build --info
+  - 'if [ "$TRAVIS_PULL_REQUEST" == "false" ]; then bash ./gradlew sonarqube --info; fi'
+
+before_cache:
+  - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
+  - rm -fr $HOME/.gradle/caches/*/plugin-resolution/
+cache:
+  directories:
+    - $HOME/.gradle/caches/
+    - $HOME/.gradle/wrapper/