Split event notification out of ev_epoll_linux.c
diff --git a/binding.gyp b/binding.gyp
index 3444fa5..3df6d0a 100644
--- a/binding.gyp
+++ b/binding.gyp
@@ -685,6 +685,7 @@
         'src/core/lib/iomgr/iomgr_uv.c',
         'src/core/lib/iomgr/iomgr_windows.c',
         'src/core/lib/iomgr/load_file.c',
+        'src/core/lib/iomgr/lockfree_event.c',
         'src/core/lib/iomgr/network_status_tracker.c',
         'src/core/lib/iomgr/polling_entity.c',
         'src/core/lib/iomgr/pollset_set_uv.c',