Use LIBCLANG_NOTHREADS instead of CINDEXTEST_NOTHREADS inside libclang,
so the c-index-test one can be enabled without affecting libclang.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@143288 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/CIndex.cpp b/tools/libclang/CIndex.cpp
index 8f0c225..61faf77 100644
--- a/tools/libclang/CIndex.cpp
+++ b/tools/libclang/CIndex.cpp
@@ -2719,7 +2719,7 @@
   ReparseTranslationUnitInfo RTUI = { TU, num_unsaved_files, unsaved_files,
                                       options, 0 };
 
-  if (getenv("CINDEXTEST_NOTHREADS")) {
+  if (getenv("LIBCLANG_NOTHREADS")) {
     clang_reparseTranslationUnit_Impl(&RTUI);
     return RTUI.result;
   }