Bazel: Add standalone build mode

Test Plan:

1. Build the plugins:

  $ bazel build :all
  INFO: Analysed target //:all (26 packages loaded).
  INFO: Found 1 target...
  Target //:all up-to-date:
    bazel-genfiles/all.zip
  INFO: Elapsed time: 1.060s, Critical Path: 0.41s

2. Verify the content is sane:

  $ unzip -t bazel-genfiles/all.zip
  Archive:  bazel-genfiles/all.zip
      testing: owners.jar               OK
      testing: owners-autoassign.jar    OK

3. Run the tests:

  $ bazel test //...
  INFO: Found 1 test target...
  Target //owners-common:test up-to-date:
    bazel-bin/owners-common/test.jar
    bazel-bin/owners-common/test
  INFO: Elapsed time: 4.941s, Critical Path: 3.18s
  INFO: Build completed successfully, 13 total actions
  //owners-common:test                           PASSED in 1.9s

4. Generate Eclipse project:

   $ tools/eclipse/project.sh
   Verify project can be imported to Eclipse and dependencies are in the
   classpath

Change-Id: I211bd5acb293a36f9c12b428fbb0a4ceb4dfc177
diff --git a/BUILD b/BUILD
new file mode 100644
index 0000000..b52c2c1
--- /dev/null
+++ b/BUILD
@@ -0,0 +1,29 @@
+load("//tools:genrule2.bzl", "genrule2")
+load("//tools/bzl:plugin.bzl", "PLUGIN_TEST_DEPS")
+load("//owners-common:common.bzl", "EXTERNAL_DEPS")
+
+genrule2(
+    name = "all",
+    srcs = [
+        "//owners",
+        "//owners-autoassign",
+        "//owners-common",
+    ],
+    outs = ["all.zip"],
+    cmd = " && ".join([
+        "cp $(SRCS) $$TMP",
+        "cd $$TMP",
+        "zip -qr $$ROOT/$@ .",
+    ]),
+)
+
+java_library(
+    name = "owners_classpath_deps",
+    testonly = 1,
+    visibility = ["//visibility:public"],
+    exports = EXTERNAL_DEPS + PLUGIN_TEST_DEPS + [
+        "//owners:owners__plugin",
+        "//owners-autoassign:owners-autoassign__plugin",
+        "//owners-common:owners-common__plugin",
+    ],
+)