Fix build, fix epollex detection
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index afab2296..b600de2 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -952,6 +952,8 @@
 src/core/lib/iomgr/error_internal.h \
 src/core/lib/iomgr/ev_epoll_linux.c \
 src/core/lib/iomgr/ev_epoll_linux.h \
+src/core/lib/iomgr/ev_epollex_linux.c \
+src/core/lib/iomgr/ev_epollex_linux.h \
 src/core/lib/iomgr/ev_poll_posix.c \
 src/core/lib/iomgr/ev_poll_posix.h \
 src/core/lib/iomgr/ev_posix.c \