Solve uv link problem
diff --git a/src/core/lib/iomgr/timer_uv.c b/src/core/lib/iomgr/timer_uv.c
index 8e8a075..3830d78 100644
--- a/src/core/lib/iomgr/timer_uv.c
+++ b/src/core/lib/iomgr/timer_uv.c
@@ -42,6 +42,9 @@
#include <uv.h>
+grpc_tracer_flag grpc_timer_trace = GRPC_TRACER_INITIALIZER(false);
+grpc_tracer_flag grpc_timer_check_trace = GRPC_TRACER_INITIALIZER(false);
+
static void timer_close_callback(uv_handle_t *handle) { gpr_free(handle); }
static void stop_uv_timer(uv_timer_t *handle) {