Split event notification out of ev_epoll_linux.c
diff --git a/build.yaml b/build.yaml
index c294fc9..c8098c5 100644
--- a/build.yaml
+++ b/build.yaml
@@ -208,6 +208,7 @@
   - src/core/lib/iomgr/iomgr_internal.h
   - src/core/lib/iomgr/iomgr_posix.h
   - src/core/lib/iomgr/load_file.h
+  - src/core/lib/iomgr/lockfree_event.h
   - src/core/lib/iomgr/network_status_tracker.h
   - src/core/lib/iomgr/polling_entity.h
   - src/core/lib/iomgr/pollset.h
@@ -320,6 +321,7 @@
   - 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