fixed oss build error related to inject_pause

Summary:
As reported by #270, the oss build is broken because we
forgot to add the newly added file inject_pause.cpp to CMakeLists.txt. This changes fixes it.
When we work on D48811189,

Reviewed By: haowu14

Differential Revision: D50618724

fbshipit-source-id: 5e29145a207ece914485beaa6f613040b49dc871

cachelib/common/CMakeLists.txt

@@ -21,6 +21,7 @@ add_library (cachelib_common
   CountDownLatch.cpp
   ${BLOOM_THRIFT_FILES}
   hothash/HotHashDetector.cpp
+  inject_pause.cpp
   PercentileStats.cpp
   PeriodicWorker.cpp
   piecewise/GenericPieces.cpp