integration: Redirect nghttpx stdout/stderr to test driver's stdout/stderr

integration-tests/server_tester.go

@@ -17,6 +17,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"os"
 	"os/exec"
 	"sort"
 	"strconv"
@@ -192,6 +193,9 @@ func newServerTesterInternal(src_args []string, t *testing.T, handler http.Handl
 		errCh:        make(chan error),
 	}
 
+	st.cmd.Stdout = os.Stdout
+	st.cmd.Stderr = os.Stderr
+
 	if err := st.cmd.Start(); err != nil {
 		st.t.Fatalf("Error starting %v: %v", serverBin, err)
 	}