ar: detect and error out on 32-bit symbol table overflow

BSD ar currently does not support the /SYM64/ 64-bit symbol table, and
previously truncated to 32-bits, silently producing corrupted archives
larger than 4GB.

This is another overflow case in addtion to r342575.

PR:		234454
Reported by:	Aijaz Baig, imp
MFC after:	2 weeks
MFC with:	r342575
Sponsored by:	The FreeBSD Foundation

usr.bin/ar/write.c

@@ -628,6 +628,9 @@ write_objs(struct bsdar *bsdar)
 		if (strlen(obj->name) > _MAXNAMELEN_SVR4)
 			add_to_ar_str_table(bsdar, obj->name);
 		bsdar->rela_off += _ARHDR_LEN + obj->size + obj->size % 2;
+		if (bsdar->rela_off > UINT32_MAX)
+			bsdar_errc(bsdar, EX_SOFTWARE, 0,
+			    "Symbol table offset overflow");
 	}
 
 	/*