setjmp/longjmp compatibility

[fuhsnn]

For example, the snippet from cppreference:

#include <stdio.h>
#include <setjmp.h>
#include <stdnoreturn.h>

jmp_buf my_jump_buffer;

noreturn void foo(int status) 
{
    printf("foo(%d) called\n", status);
    longjmp(my_jump_buffer, status + 1); // will return status+1 out of setjmp
}

int main(void)
{
    volatile int count = 0; // modified local vars in setjmp scope must be volatile
    if (setjmp(my_jump_buffer) != 5) // compare against constant in an if
        foo(++count);
}

chibicc compiled code executes like an infinite loop.