Add iperf server

Change-Id: I2cd24b04013a03e9e4e643d29a813bdf7d3e87e3
diff --git a/BUILD.gn b/BUILD.gn
index 9ff1c29..2588b2b 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -14,6 +14,7 @@
     "ports/fuchsia/include/netif/ethernetif.h",
     "ports/fuchsia/netif/ethernetif.c",
     "ports/fuchsia/sys_arch.c",
+    "src/apps/lwiperf/lwiperf.c",
     "src/api/api_lib.c",
     "src/api/api_msg.c",
     "src/api/err.c",