Configure CMake, add macOS placeholder

Add flags for determining generator platform.

CMakeLists.txt

@@ -3,4 +3,18 @@ project(cerberus C)
 
 set(CMAKE_C_STANDARD 11)
 
-add_executable(cerberus WIN32 src/main.c)
+if (WIN32)
+    # TODO set arch on target instead of generator
+    if (CMAKE_SIZEOF_VOID_P EQUAL 8)
+        set(PROJECT_ARCH x64)
+        add_definitions(-DWIN64)
+    else ()
+        set(PROJECT_ARCH x86)
+        add_definitions(-DWIN32)
+    endif ()
+    add_executable(cerberus WIN32 src/main.c)
+elseif(APPLE)
+    add_definitions(-DMACOS)
+elseif(UNIX)
+    add_definitions(-DUNIX)
+endif ()

src/main.c

@@ -1,3 +1,5 @@
+#ifdef WIN64
+
 #include <windows.h>
 
 LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
@@ -48,3 +50,9 @@ LRESULT CALLBACK WndProc(HWND hwnd, UINT msg,
 
 	return DefWindowProcW(hwnd, msg, wParam, lParam);
 }
+
+#elif defined MACOS
+
+// https://stackoverflow.com/questions/30269329/creating-window-application-in-pure-c-on-mac-osx
+
+#endif