Bazel: Produce headless war

This change creates the archive with:

lib
pgm-lib
default web assets

but without:

GWT UI
PolyGerrit UI
Plugins
Documentation

TEST PLAN:

  bazel build :headless
  java -jar bazel-bin/headless.war init -d ../test_site_bazel

Change-Id: I53987b10a5863aee0298bd2ea29405c26dbacb0c

BUILD

@@ -1,4 +1,5 @@
 load('//tools/bzl:genrule2.bzl', 'genrule2')
+load('//tools/bzl:pkg_war.bzl', 'pkg_war')
 
 genrule2(
   name = 'version',
@@ -7,3 +8,21 @@ genrule2(
   out = 'version.txt',
   visibility = ['//visibility:public'],
 )
+
+pkg_war(
+  name = 'headless',
+  context = [
+    '//gerrit-main:main_bin_deploy.jar',
+    '//gerrit-war:webapp_assets',
+  ],
+  libs = [
+    '//gerrit-war:init',
+    '//gerrit-war:log4j-config',
+    '//gerrit-war:version',
+    '//lib:postgresql',
+    '//lib/log:impl_log4j',
+  ],
+  pgmlibs = [
+    '//gerrit-pgm:pgm'
+  ],
+)