Added JDK11

JDK11 was added in third_party/openjdk for Mac/Linux/Win
so that we can perform test with the jdk11 compiler
Next CL will introduce the JDK11 support in the Tests
Currently jdk11 is not used in the code base.

In GCloud, the following README.google file was added:

Name: OpenJDK 11 GA
URL: https://openjdk.java.net/
Version: 11 GA
Revision: NA
Date: April 12 2019
License: The GNU General Public License (GPL) (see legal/**/LICENSE)

Description:
This is a copy of the OpenJDK 11 GA distributed at https://jdk.java.net/archive/,
Source is available at https://hg.openjdk.java.net/jdk/jdk11/
but where all the legal symlinks were removed by duplicating licence files.

Change-Id: I558bf63b2b47649a9869b392d9edc061380d03c4
diff --git a/build.gradle b/build.gradle
index 4b8b793..b448ea2 100644
--- a/build.gradle
+++ b/build.gradle
@@ -304,14 +304,17 @@
 def cloudSystemDependencies = [
         linux: [
                 "third_party": ["openjdk/openjdk-9.0.4/linux",
-                                "openjdk/jdk8/linux-x86"],
+                                "openjdk/jdk8/linux-x86",
+                                "openjdk/jdk-11/Linux"],
         ],
         osx: [
                 "third_party": ["openjdk/openjdk-9.0.4/osx",
-                                "openjdk/jdk8/darwin-x86"],
+                                "openjdk/jdk8/darwin-x86",
+                                "openjdk/jdk-11/Mac"],
         ],
         windows: [
-                "third_party": ["openjdk/openjdk-9.0.4/windows"],
+                "third_party": ["openjdk/openjdk-9.0.4/windows",
+                                "openjdk/jdk-11/Windows"],
         ],
 ]