Adapt regalloc2-tool to work with creduce

The fuzzing strategy we use for regalloc2 doesn't minimize well, which can make isolating a failure somewhat tedious. If the textual format emitted by regalloc2-tool looked enough like c to be used with `creduce`, we could write a script to automate minimization by using creduce to shrink the input.

首先定位 regalloc2-tool 生成的文本格式，并查看 creduce 如何使用输入。确定需要进行哪些更改，才能使输出足够类似 C，然后验证脚本是否可以使用 creduce 来最小化一个失败的 regalloc2 输入。

由索引模型根据 Issue 内容生成。