Switch to using WAPP_PLATFORM_CPP instead of __cplusplus

src/core/mem/arena/mem_arena.h

@@ -2,12 +2,13 @@
 #define MEM_ARENA_H
 
 #include "../../../common/aliases/aliases.h"
+#include "../../../common/platform/platform.h"
 #include "../../os/mem/mem_os.h"
 #include <stdbool.h>
 
-#ifdef __cplusplus
+#ifdef WAPP_PLATFORM_CPP
 BEGIN_C_LINKAGE
-#endif // __cplusplus
+#endif // WAPP_PLATFORM_CPP
 
 typedef struct arena Arena;
 
@@ -33,8 +34,8 @@ void *wapp_mem_arena_realloc_aligned(Arena *arena, void *ptr, u64 old_size, u64
 void wapp_mem_arena_clear(Arena *arena);
 void wapp_mem_arena_destroy(Arena **arena);
 
-#ifdef __cplusplus
+#ifdef WAPP_PLATFORM_CPP
 END_C_LINKAGE
-#endif // __cplusplus
+#endif // WAPP_PLATFORM_CPP
 
 #endif // !MEM_ARENA_H