examples: fix prerequisites for debian

Change-Id: I760a2dd1b54101aed2405d005fb699800dc0059b
Reviewed-on: https://weave-review.googlesource.com/1481
Reviewed-by: Johan Euphrosine <proppy@google.com>
diff --git a/examples/provider/wifi_manager.cc b/examples/provider/wifi_manager.cc
index 6e216e4..ed6a9fd 100644
--- a/examples/provider/wifi_manager.cc
+++ b/examples/provider/wifi_manager.cc
@@ -42,7 +42,7 @@
 
 WifiImpl::WifiImpl(provider::TaskRunner* task_runner, EventNetworkImpl* network)
     : task_runner_{task_runner}, network_{network} {
-  CHECK_EQ(0, getuid())
+  CHECK_EQ(0u, getuid())
       << "WiFi manager expects root access to control WiFi capabilities";
   StopAccessPoint();
 }