backgammon(6): Prevent LTO seeing details for now.

backgammon(6): Prevent LTO seeing details for now.

init.c should contain "back.h" for types (TBI later).
-flto gives lots of error: type of 'args' does not match original declaration [-Werror]

/usr/src/games/backgammon/backgammon/../common_source/back.h
 extern char *args[16]; /* args passed to teachgammon and back */
/usr/src/games/backgammon/backgammon/../common_source/init.c
 char args[100];

/usr/src/games/backgammon/backgammon/../common_source/back.h
 extern int  old; /* original tty status */
/usr/src/games/backgammon/backgammon/../common_source/init.c
 struct termios tty, old, noech, raw;

/usr/src/games/backgammon/backgammon/../common_source/back.h
 extern int  raw; /* raw tty status, no echo */
/usr/src/games/backgammon/backgammon/../common_source/init.c
 struct termios tty, old, noech, raw;

/usr/src/games/backgammon/backgammon/../common_source/back.h
 extern int  noech; /* original tty status without echo */
/usr/src/games/backgammon/backgammon/../common_source/init.c
 struct termios tty, old, noech, raw;
lto1: all warnings being treated as errors