Fix for -fno-common
https://gitlab.com/LibreGames/jumpnbump/-/commit/b72b70a4233776bdaa6a683c89af2becefd53bd6.diff

Index: globals.pre
--- globals.pre.orig
+++ globals.pre
@@ -267,7 +267,7 @@ extern gob_t number_gobs;
 
 /* main.c */
 
-int endscore_reached;
+extern int endscore_reached;
 
 void steer_players(void);
 void position_player(int player_num);
