[c-index-test] CMake: add missing reference to clangSerialization library.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@293466 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/c-index-test/CMakeLists.txt b/tools/c-index-test/CMakeLists.txt
index b845af0..7244e2c 100644
--- a/tools/c-index-test/CMakeLists.txt
+++ b/tools/c-index-test/CMakeLists.txt
@@ -27,6 +27,7 @@
     clangCodeGen
     clangFrontend
     clangIndex
+    clangSerialization
   )
 endif()