Make sure the LLVMContext outlive the CompilerInstance

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266277
diff --git a/clang/unittests/CodeGen/BufferSourceTest.cpp b/clang/unittests/CodeGen/BufferSourceTest.cpp
index 56aafce..1934e66 100644
--- a/clang/unittests/CodeGen/BufferSourceTest.cpp
+++ b/clang/unittests/CodeGen/BufferSourceTest.cpp
@@ -39,8 +39,8 @@
     "EmitCXXGlobalInitFunc test;    ";
 
 TEST(BufferSourceTest, EmitCXXGlobalInitFunc) {
-    CompilerInstance compiler;
     LLVMContext Context;
+    CompilerInstance compiler;
 
     compiler.createDiagnostics();
     compiler.getLangOpts().CPlusPlus = 1;