llama2c : fix basename on Windows

examples/convert-llama2c-to-ggml/convert-llama2c-to-ggml.cpp

@@ -902,7 +902,7 @@ bool params_parse(int argc, char ** argv, struct train_params * params) {
 }
 
 std::string basename(const std::string &path) {
-    size_t pos = path.find_last_of("/");
+    size_t pos = path.find_last_of("/\\");
     if (pos == std::string::npos) {
         return path;
     }