Set JAVA_HOME before forking setup commands (#29647)

Today when forking setup commands we do not set JAVA_HOME. This means
that we might not use a version of Java compatible with the version of
Java the command is expecting to run on (for example, 5.6 nodes would
expect JDK 8, and this is true even for their setup commands). This
commit sets JAVA_HOME when configuring setup command tasks.

buildSrc/src/main/groovy/org/elasticsearch/gradle/test/ClusterFormationTasks.groovy

@@ -567,16 +567,17 @@ class ClusterFormationTasks {
 
     /** Adds a task to execute a command to help setup the cluster */
     static Task configureExecTask(String name, Project project, Task setup, NodeInfo node, Object[] execArgs) {
-        return project.tasks.create(name: name, type: LoggedExec, dependsOn: setup) {
-            workingDir node.cwd
+        return project.tasks.create(name: name, type: LoggedExec, dependsOn: setup) { Exec exec ->
+            exec.workingDir node.cwd
+            exec.environment 'JAVA_HOME', node.getJavaHome()
             if (Os.isFamily(Os.FAMILY_WINDOWS)) {
-                executable 'cmd'
-                args '/C', 'call'
+                exec.executable 'cmd'
+                exec.args '/C', 'call'
                 // On Windows the comma character is considered a parameter separator:
                 // argument are wrapped in an ExecArgWrapper that escapes commas
-                args execArgs.collect { a -> new EscapeCommaWrapper(arg: a) }
+                exec.args execArgs.collect { a -> new EscapeCommaWrapper(arg: a) }
             } else {
-                commandLine execArgs
+                exec.commandLine execArgs
             }
         }
     }