-fno-common

Index: src/variable.h
--- src/variable.h.orig
+++ src/variable.h
@@ -116,7 +116,6 @@ struct pattern_var
 extern char *variable_buffer;
 extern struct variable_set_list *current_variable_set_list;
 extern struct variable *default_goal_var;
-extern struct variable shell_var;
 
 /* expand.c */
 #ifndef SIZE_MAX