message: Fix the instructions for C++ hello world example.
diff: @@ -12,13 +12,22 @@ obtaining a primitive, and using the primitive to do crypto.
  ### Bazel
  ```shell
  +# Build the code.
  git clone https://github.com/google/tink
  -cd tink
  +cd tink/examples/cc
  bazel build ...
  +
  +# Create some input.
  echo "some plaintext" > foo.txt
  -./bazel-bin/examples/helloworld/cc/hello_world ./examples/helloworld/cc/aes128_gcm_test_keyset_json.txt\
  - encrypt foo.txt "some aad" bar.encrypted
  -./bazel-bin/examples/helloworld/cc/hello_world ./examples/helloworld/cc/aes128_gcm_test_keyset_json.txt\
  - decrypt bar.encrypted "some aad" foo-decrypted.txt
  +
  +# Encrypt.
  +./bazel-bin/helloworld/hello_world ./helloworld/aes128_gcm_test_keyset_json.txt \
  + encrypt foo.txt "some aad" foo.encrypted
  +
  +# Decrypt.
  +./bazel-bin/helloworld/hello_world ./helloworld/aes128_gcm_test_keyset_json.txt \
  + decrypt foo.encrypted "some aad" foo-decrypted.txt
  +
  +# Inspect the output.
  cat foo-decrypted.txt
  ```
  