chore: import upstream snapshot with attribution

cpp/base.h

@@ -0,0 +1,16 @@
+/*!
+ *  Copyright (c) 2023-2025 by Contributors
+ * \file base.h
+ */
+
+#ifndef MLC_LLM_DLL
+#ifdef _WIN32
+#ifdef MLC_LLM_EXPORTS
+#define MLC_LLM_DLL __declspec(dllexport)
+#else
+#define MLC_LLM_DLL __declspec(dllimport)
+#endif
+#else
+#define MLC_LLM_DLL __attribute__((visibility("default")))
+#endif
+#endif