Switch to using a CAS loop to update the token value.
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index 2fb00a3..c78e4a7 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -211,6 +211,7 @@
                       'src/core/lib/profiling/basic_timers.c',
                       'src/core/lib/profiling/stap_timers.c',
                       'src/core/lib/support/alloc.c',
+                      'src/core/lib/support/atm.c',
                       'src/core/lib/support/avl.c',
                       'src/core/lib/support/backoff.c',
                       'src/core/lib/support/cmdline.c',