Code style: add missed explicit 'this->'

CMake uses explicit 'this->' style. Using custom clang-tidy check we can
detect and fix places where 'this->' was missed.

Source/cmListFileCache.h

@@ -249,7 +249,7 @@ public:
   BTs(T v = T(), cmListFileBacktrace bt = cmListFileBacktrace())
     : Value(std::move(v))
   {
-    Backtraces.emplace_back(std::move(bt));
+    this->Backtraces.emplace_back(std::move(bt));
   }
   T Value;
   std::vector<cmListFileBacktrace> Backtraces;