add player_field_avatar.c

ld_script.txt

@@ -91,6 +91,7 @@ SECTIONS {
         src/metatile_behavior.o(.text);
         src/field_camera.o(.text);
         src/field_door.o(.text);
+        src/field_player_avatar.o(.text);
         asm/field_player_avatar.o(.text);
         src/event_object_movement.o(.text);
         src/field_message_box.o(.text);