Create war artifact

web.xml is restored from: Ib8f187039.  Ths commit partially reverts
f54665e0a0ec4025fa01d79911ff5ae4e88fc19f.

Test Plan:

  $ bazel build gitiles
  $ unzip -t bazel-bin/gitiles.war

Change-Id: I9778da62b06b357c718275837a3df95ca0043562

BUILD

diff --git a/BUILD b/BUILD
index d2e59f3..773eb61 100644
--- a/BUILD
+++ b/BUILD
@@ -1 +1,13 @@
-# This file is intended to be empty
+load("@com_googlesource_gerrit_bazlets//tools:pkg_war.bzl", "pkg_war")
+
+pkg_war(
+    name = "gitiles",
+    context = ["//gitiles-servlet:webassets"],
+    libs = [
+        "//gitiles-servlet:servlet",
+        "//lib/jetty:server",
+        "//lib/jetty:servlet",
+        "//lib/slf4j:slf4j-simple",
+    ],
+    web_xml = "//gitiles-war:web_xml",
+)