Open-source Bazel integration tests

It is a first batch of integration tests for Bazel. They tests some
basic behaviors and nominal cases of Bazel rules (especially they tests
the behavior of the examples provided in //examples).

--
MOS_MIGRATED_REVID=89440074
diff --git a/examples/BUILD b/examples/BUILD
new file mode 100644
index 0000000..5551cb2
--- /dev/null
+++ b/examples/BUILD
@@ -0,0 +1,15 @@
+package(default_visibility = ["//visibility:public"])
+
+filegroup(
+    name = "srcs",
+    srcs = [
+        "//examples/cpp:srcs",
+        "//examples/gen:srcs",
+        "//examples/go:srcs",
+        "//examples/java-native:srcs",
+        "//examples/java-skylark:srcs",
+        "//examples/objc:srcs",
+        "//examples/proto:srcs",
+        "//examples/py:srcs",
+    ],
+)