make it compiler

src/link.c

@@ -28,6 +28,8 @@
 #include "link.h"
 #include "link_rfu.h"
 
+extern u16 gUnknown_03005DA8;
+
 // Static type declarations
 
 struct BlockTransfer

src/link_rfu.c

@@ -16,6 +16,8 @@
 #include "rom_8011DC0.h"
 #include "link_rfu.h"
 
+extern u16 gUnknown_03005DA8;
+
 // Static type declarations
 
 // Static RAM declarations