Add jvmArgs '-Xshare:off' for Gradle test tasks

There is an extra warning in the build logs:
```
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
```
which we cannot mitigate since we fork JVM for every module, and it tries to share & amend classpath for every module

(We can revert this fix eventually, if we find it causing performance degradation)

Author: artembilan

build.gradle

@@ -336,6 +336,8 @@ configure(javaProjects) { subproject ->
         reports.junitXml.required = false
 
         enableAssertions = false
+
+        jvmArgs '-Xshare:off'
     }
 
     checkstyle {