Fix CMake build: EventBaseTestLib.cpp doesn't exist (#1284)

Summary:
- EventBaseTestLib.cpp file was moved to EventBaseTestLibProvider.cpp
  in Differential Revision: D19001877.
- Change CMakeLists.txt to specify EventBaseTestLibProvider.cpp so that
  CMake does not fail at configure time due to EventBaseTestLib.cpp not
  existing in the source tree.
Pull Request resolved: https://github.com/facebook/folly/pull/1284

Reviewed By: markisaa

Differential Revision: D19226798

Pulled By: yfeldblum

fbshipit-source-id: 45a5e5ca03a52897a6f8f711761bf78ef386e6f6

CMakeLists.txt

@@ -723,7 +723,7 @@ if (BUILD_TESTS)
       TEST DelayedDestructionTest SOURCES DelayedDestructionTest.cpp
       TEST DelayedDestructionBaseTest SOURCES DelayedDestructionBaseTest.cpp
       TEST DestructorCheckTest SOURCES DestructorCheckTest.cpp
-      TEST EventBaseTest SOURCES EventBaseTest.cpp EventBaseTestLib.cpp
+      TEST EventBaseTest SOURCES EventBaseTest.cpp EventBaseTestLibProvider.cpp
       TEST EventBaseLocalTest SOURCES EventBaseLocalTest.cpp
       TEST HHWheelTimerTest SOURCES HHWheelTimerTest.cpp
       TEST HHWheelTimerSlowTests SLOW