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

gitiles-servlet/BUILD

diff --git a/gitiles-servlet/BUILD b/gitiles-servlet/BUILD
index 94ddc8e..127608b 100644
--- a/gitiles-servlet/BUILD
+++ b/gitiles-servlet/BUILD
@@ -1,3 +1,8 @@
+load(
+    "@com_googlesource_gerrit_bazlets//tools:genrule2.bzl",
+    "genrule2",
+)
+
 DEPS = [
     "//blame-cache:lib",
     "//lib:autolink",
@@ -38,6 +43,20 @@
     ],
 )
 
+genrule2(
+    name = "webassets",
+    srcs = glob(["src/main/resources/com/google/gitiles/static/**/*"]),
+    outs = ["webassets.zip"],
+    cmd = " && ".join([
+        "o=$$PWD/$@",
+        "tar cf - $(SRCS) | tar -C $$TMP/ --strip-components=2 -xf -",
+        "cd $$TMP/main/resources/com/google/gitiles/",
+        "mv static +static",
+        "zip -qr $$o .",
+    ]),
+    visibility = ["//visibility:public"],
+)
+
 java_library(
     name = "testutil",
     srcs = glob(