Add support for Gerrit 3.9.9

Change-Id: Ia67551be2995653baf5d6f559334194248df8cfd

gerrit@3.9.9.rb

diff --git a/gerrit@3.9.9.rb b/gerrit@3.9.9.rb
new file mode 100644
index 0000000..cbb35de
--- /dev/null
+++ b/gerrit@3.9.9.rb
@@ -0,0 +1,18 @@
+# typed: false
+# frozen_string_literal: true
+
+require_relative 'gerritbase'
+
+class GerritAT399 < GerritBase
+
+  def self.java_version
+    "17"
+  end
+
+  set_common_dependencies
+
+  version "3.9.9"
+  sha256 "373f242b1105af584719d0573ea1d89efa4f77bd606407a5ce2d17501a1da058"
+  url generate_url(version)
+
+end