Add OpenJDK 18 (ea+33)

Content of README.google:

Name: Java Development Kit (JDK)
URL: https://jdk.java.net/17/
Version: 18+ea-33
Revision: NA
License: the GNU General Public License, version 2, with the Classpath Exception.

Description:
This is pulled directly from the website for the JDK releases that has an open source license.
Synlinks have reen resolved using `cp -rL` before uploading.
Change-Id: I9cba1173fd4edb3e387056af6c2c897c7f885f18
diff --git a/.gitignore b/.gitignore
index 17af682..b9fc551 100644
--- a/.gitignore
+++ b/.gitignore
@@ -135,32 +135,12 @@
 third_party/openjdk/desugar_jdk_libs_releases/1.1.1.tar.gz
 third_party/openjdk/desugar_jdk_libs_releases/1.1.5
 third_party/openjdk/desugar_jdk_libs_releases/1.1.5.tar.gz
-third_party/openjdk/jdk-17/linux
-third_party/openjdk/jdk-17/linux.tar.gz
-third_party/openjdk/jdk-17/osx
-third_party/openjdk/jdk-17/osx.tar.gz
-third_party/openjdk/jdk-17/windows
-third_party/openjdk/jdk-17/windows.tar.gz
-third_party/openjdk/jdk-16/linux
-third_party/openjdk/jdk-16/linux.tar.gz
-third_party/openjdk/jdk-16/osx
-third_party/openjdk/jdk-16/osx.tar.gz
-third_party/openjdk/jdk-16/windows
-third_party/openjdk/jdk-16/windows.tar.gz
-third_party/openjdk/jdk-15/linux
-third_party/openjdk/jdk-15/linux.tar.gz
-third_party/openjdk/jdk-15/osx
-third_party/openjdk/jdk-15/osx.tar.gz
-third_party/openjdk/jdk-15/windows
-third_party/openjdk/jdk-15/windows.tar.gz
-third_party/openjdk/jdk-11-test
-third_party/openjdk/jdk-11-test.tar.gz
-third_party/openjdk/jdk-11/linux
-third_party/openjdk/jdk-11/linux.tar.gz
-third_party/openjdk/jdk-11/osx
-third_party/openjdk/jdk-11/osx.tar.gz
-third_party/openjdk/jdk-11/windows
-third_party/openjdk/jdk-11/windows.tar.gz
+third_party/openjdk/jdk-[0-9][0-9]/linux
+third_party/openjdk/jdk-[0-9][0-9]/linux.tar.gz
+third_party/openjdk/jdk-[0-9][0-9]/osx
+third_party/openjdk/jdk-[0-9][0-9]/osx.tar.gz
+third_party/openjdk/jdk-[0-9][0-9]/windows
+third_party/openjdk/jdk-[0-9][0-9]/windows.tar.gz
 third_party/openjdk/jdk8/darwin-x86
 third_party/openjdk/jdk8/darwin-x86.tar.gz
 third_party/openjdk/jdk8/linux-x86