Switch to using a CAS loop to update the token value.
diff --git a/build.yaml b/build.yaml
index ae546cb..7b27968 100644
--- a/build.yaml
+++ b/build.yaml
@@ -101,6 +101,7 @@
   - 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