pw_transfer: Python & C++ integration test

Basic tests for transmitting data between a Python client and a C++
server using pw_transfer.

Change-Id: I75c361ec100b055e0d6afb0091e64cc9d773c568
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/54707
Commit-Queue: Wyatt Hepler <hepler@google.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Reviewed-by: Alexei Frolov <frolv@google.com>
diff --git a/pw_transfer/BUILD.gn b/pw_transfer/BUILD.gn
index 679af62..37f7a5c 100644
--- a/pw_transfer/BUILD.gn
+++ b/pw_transfer/BUILD.gn
@@ -81,3 +81,13 @@
   sources = [ "docs.rst" ]
   inputs = [ "transfer.proto" ]
 }
+
+pw_executable("test_rpc_server") {
+  sources = [ "test_rpc_server.cc" ]
+  deps = [
+    ":pw_transfer",
+    "$dir_pw_rpc/system_server",
+    "$dir_pw_rpc/system_server:socket",
+    dir_pw_log,
+  ]
+}