README: fix gyp command line

Change-Id: Id51e77b7ac193fd777a43c1fd0943708a112eeb3
Reviewed-on: https://weave-review.googlesource.com/1324
Reviewed-by: Vitaly Buka <vitalybuka@google.com>
1 file changed
tree: e771e8574bafd2000e23f750fde2ed18a2f01721
  1. libweave/