1) Do not use gflags in the example binary code.

2) Also surface wv_cas_key_fetcher_example to partner.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=229965302

example/BUILD

@@ -18,8 +18,10 @@ filegroup(
     srcs = [
         "test_ecmg_messages.h",
         "wv_cas_ecm_example.cc",
+        "wv_cas_key_fetcher_example.cc",
         "wv_cas_types_example.cc",
         ":wv_cas_ecm_example",
+        ":wv_cas_key_fetcher_example",
         ":wv_cas_types_example",
     ],
 )