Fix BUILD
diff --git a/BUILD b/BUILD
index ca0a1c5..47017bf 100644
--- a/BUILD
+++ b/BUILD
@@ -308,6 +308,7 @@
     srcs = [
         "src/core/lib/profiling/basic_timers.c",
         "src/core/lib/profiling/stap_timers.c",
+        "src/core/lib/support/arena.c",
         "src/core/lib/support/alloc.c",
         "src/core/lib/support/avl.c",
         "src/core/lib/support/backoff.c",
@@ -352,6 +353,7 @@
         "src/core/lib/support/wrap_memcpy.c",
     ],
     hdrs = [
+        "src/core/lib/support/arena.h",
         "src/core/lib/profiling/timers.h",
         "src/core/lib/support/backoff.h",
         "src/core/lib/support/block_annotate.h",