allow ` escaping in Gui commands

src/build/parser.cr

@@ -140,7 +140,7 @@ module Build
  # Gui accepts many subcommands. Instead of duplicating parsing logic into a generic
  # `Gui` cmd, instead join together (e.g. `GuiAdd`) and parse line again with that.
  # All subcommands exist as standalone commands and expect the gui id as 1st arg.
- split = split_args(args, 2)
+ split = args.split(',', 2).map &.strip
  sub_instruction = split[0]? || ""
  rest_args = split[1]? || ""
  match = sub_instruction.match(/(?:(\S+)\s*:\s*)?(.*)/).not_nil!