[libclang] Make sure Preprocessor is set in ASTUnit during indexing.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@148319 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/Indexing.cpp b/tools/libclang/Indexing.cpp
index 630c55b..6bffc6b 100644
--- a/tools/libclang/Indexing.cpp
+++ b/tools/libclang/Indexing.cpp
@@ -176,6 +176,7 @@
     IndexCtx.setASTContext(CI.getASTContext());
     Preprocessor &PP = CI.getPreprocessor();
     PP.addPPCallbacks(new IndexPPCallbacks(PP, IndexCtx));
+    IndexCtx.setPreprocessor(PP);
     return new IndexingConsumer(IndexCtx);
   }