__builtin_elementwise_pow breaks with .yyy swizzle from const pointer

couldn't really think of a better way to describe the bug. here's the repro code:
```c
typedef float vec3 __attribute__((ext_vector_type(3)));

typedef struct {
    vec3 b;
} struc;

vec3 foo(vec3 a, const struc* hi) { // <- remove const and it'll compile

    vec3 b = __builtin_elementwise_max((vec3)(0.0f), a);
    
    return __builtin_elementwise_pow(b, hi->b.yyy);
}
```