When GDB/MI includes script information in `-break-info`, it violates
its own syntax by wrapping script field value in curly braces (like
for tuples) instead of brackets (like for lists, which should be the
case for script listing), for example:

script={"silent","xgetptr Vinitial_window_system","set $tem = ( struct
Lisp_Symbol *) $ptr","xgetptr $tem->xname","set $tem = (struct
Lisp_String *) $ptr","set $tem = (char *) $tem->data","if $tem[0] ==
'x' && $tem[1] == '\0'","break x_error_quitter","end","continue"}

Whereas according to GDB/MI Output Syntax tuples (enclosed in {}) may
contain only variable=value pairs.

In Emacs, I just replace braces with brackets and parse it like a list.
Not a serious bug, just a nuisance.