if/else-if/else chains and nested conditionals emit as a single
chained `if () { } else if () { } else { }` c block.

<<<

classify = fun (n int) int {
    if n < 0 {
        return -1
    } else if n == 0 {
        return 0
    } else {
        return 1
    }
}

main = fun () {
    classify(5)
}

>>>

#include "core.c"
integer classify(integer n);
void catskill_main(void);
integer classify(integer n) {
    if (n < 0) {
        return -1;
    } else if (n == 0) {
        return 0;
    } else {
        return 1;
    }
}
void catskill_main(void) {
    classify(5);
}
#include "runtime.c"