folly: cmake: enable DistributedMutexTest.cpp

Summary:
was trying to see if I could repro the issue described here:

Refs: https://github.com/facebook/folly/issues/1092

Reviewed By: yfeldblum

Differential Revision: D14702579

fbshipit-source-id: d90cbf5742883a26d9ac5dbfd56eed1965cbc64e

CMakeLists.txt

@@ -739,6 +739,7 @@ if (BUILD_TESTS)
     DIRECTORY synchronization/test/
       TEST baton_test SOURCES BatonTest.cpp
       TEST call_once_test SOURCES CallOnceTest.cpp
+      TEST distributed_mutex_test SOURCES DistributedMutexTest.cpp
       TEST lifo_sem_test SOURCES LifoSemTests.cpp
       TEST rw_spin_lock_test SOURCES RWSpinLockTest.cpp