C++: Add a test for the static local compiler-generated variable that's generated by the frontend on empty parameter packs.

Author: MathiasVP

cpp/ql/test/library-tests/compiler_generated/compilerGenerated.expected

@@ -21,5 +21,9 @@
 | cpp.cpp:19:26:19:44 | initializer for __PRETTY_FUNCTION__ | Initializer |
 | cpp.cpp:19:26:19:44 | void uses_pretty_function() | Expr |
 | cpp.cpp:20:1:20:1 | return ... | Stmt |
+| cpp.cpp:23:29:23:32 | args | Variable |
+| cpp.cpp:23:37:23:37 | return ... | Stmt |
+| cpp.cpp:23:37:23:37 | return ... | Stmt |
+| cpp.cpp:27:1:27:1 | return ... | Stmt |
 | file://:0:0:0:0 | operator delete | Function |
 | file://:0:0:0:0 | operator new | Function |

cpp/ql/test/library-tests/compiler_generated/cpp.cpp

@@ -17,4 +17,11 @@ void g1(void) {
 
 void uses_pretty_function() {
     const char* pretty = __PRETTY_FUNCTION__;
+}
+
+template <typename... Args>
+void parameter_pack(Args... args) { }
+
+void test_parameter_pack() {
+  parameter_pack();
 }