add pflag
diff --git a/third_party/spf13/pflag/README.google b/third_party/spf13/pflag/README.google
new file mode 100644
index 0000000..b899f23
--- /dev/null
+++ b/third_party/spf13/pflag/README.google
@@ -0,0 +1,3 @@
+pflag is a set of better command-line parsing utilities.
+
+URL: https://github.com/spf13/pflag.git