Append the output of the test clients to both `test.out` and `stdout`.

Examples/Echo/PackageManager/Makefile

@@ -5,10 +5,10 @@ all:
 
 test:	all
 	./Echo serve & /bin/echo $$! > echo.pid
-	./Echo get > test.out
-	./Echo expand >> test.out
-	./Echo collect >> test.out
-	./Echo update >> test.out
+	./Echo get | tee test.out
+	./Echo expand | tee -a test.out
+	./Echo collect | tee -a test.out
+	./Echo update | tee -a test.out
 	kill -9 `cat echo.pid`
 	diff test.out test.gold