[autotools->cmake] Move add_subdirectory(test) inside CLANG_INCLUDE_TESTS to match the behavior of the LLVM where LLVM_INCLUDE_TESTS controls whether tests is included.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188760 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 54ec745..e6863b2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -320,9 +320,9 @@
        ${LLVM_INCLUDE_TESTS})
 
 # TODO: docs.
-add_subdirectory(test)
 
 if( CLANG_INCLUDE_TESTS )
+  add_subdirectory(test)
   add_subdirectory(unittests)
 endif()