Places new line to reduce miscompilation.

execute.py

@@ -117,7 +117,7 @@ def process_case(target, candidate, reference, result, cppstd):
 
 def unsafe_execute_cpp(candidate, reference, result, timeout, cppstd):
     with create_tempdir():
-        code = "#include <bits/stdc++.h>\n" + candidate + reference
+        code = "#include <bits/stdc++.h>\n" + candidate + "\n" + reference
         open(f"test.cpp", "w").write(code)
 
         cpp_compiler = os.getenv("GENERICIFY_CLANG")