self.sh modifies source files for chibicc so that they are
more friendly for self-hosting. The script is used to create
a chibicc binary that consists of object files partly genearted
by gcc and the others by chibicc.

chibicc can now compile main.c and type.c with the script.

`foo(void)` indicate that function foo does not take a parameter.

A global variable can be initialized with an address of other global
variable, so the following code is legal.

  int x[3];
  int &y = x;

In addition to that, an address can have an addend, so the following
code is also legal

  int x[3];
  int &y = x+2;

So that you can write something like `int x[] = {1, 2, 3}`
instead of `int x[3] = {1, 2, 3}`.