Adjusted build staging so that engine post-build codgen wont occur when process is running

+ some refactoring as what I was doing didn't correlate to platform so I associate it with the engine module proper now.

project/engine/engine.cpp

@@ -1,6 +1,6 @@
 //#include "win32.h"
 #include "engine.hpp"
-#include "platform/platform_engine_api.hpp"
+#include "engine_to_platform_api.hpp"
 #include "handmade.hpp"
 
 NS_ENGINE_BEGIN

project/engine/engine_to_platform_api.hpp

@@ -0,0 +1,47 @@
+/*
+	This represents the API only accessible to the platform layer to fullfill for the engine layer.
+*/
+#pragma once
+#include "engine/engine.hpp"
+
+#ifndef Engine_API
+#	define Engine_API
+#endif
+
+NS_ENGINE_BEGIN
+
+using OnModuleRelaodFn = void( Memory* memory, platform::ModuleAPI* platform_api );
+using StartupFn        = void( Memory* memory, platform::ModuleAPI* platform_api );
+using ShutdownFn       = void( Memory* memory, platform::ModuleAPI* platform_api );
+
+// Needs a contextual reference to four things:
+// Timing, Input, Bitmap Buffer
+using UpdateAndRenderFn = void ( InputState* input, OffscreenBuffer* back_buffer, Memory* memory, platform::ModuleAPI* platform_api );
+
+// Audio timing is complicated, processing samples must be done at a different period from the rest of the engine's usual update.
+// IMPORTANT: This has very tight timing, and cannot be more than a millisecond in execution.
+// TODO(Ed) : Reduce timing pressure on performance by measuring it or pinging its time.
+using UpdateAudioFn = void ( AudioBuffer* audio_buffer, Memory* memory, platform::ModuleAPI* platform_api );
+
+struct ModuleAPI
+{
+	enum : u32
+	{
+		Sym_OnModuleReload,
+		Sym_Startup,
+		Sym_Shutdown,
+		Sym_UpdateAndRender,
+		Sym_UpdateAudio,
+	};
+
+	OnModuleRelaodFn* on_module_reload;
+	StartupFn*        startup;
+	ShutdownFn*       shutdown;
+
+	UpdateAndRenderFn* update_and_render;
+	UpdateAudioFn*     update_audio;
+
+	b32 IsValid;
+};
+
+NS_ENGINE_END