Switch from using a lit.cfg-generator variable that happens to be found
due to strange scoping rules to the actual canonical variable name
within the LLVM CMake build.

No functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159575 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/cmake/modules/AddLLVM.cmake b/cmake/modules/AddLLVM.cmake
index b5a5c83..78a21ad 100755
--- a/cmake/modules/AddLLVM.cmake
+++ b/cmake/modules/AddLLVM.cmake
@@ -259,7 +259,7 @@
   separate_arguments(LIT_ARGS)
   set(LIT_COMMAND
     ${PYTHON_EXECUTABLE}
-    ${LLVM_SOURCE_DIR}/utils/lit/lit.py
+    ${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py
     --param build_config=${CMAKE_CFG_INTDIR}
     --param build_mode=${RUNTIME_BUILD_MODE}
     ${LIT_ARGS}