Custom derives on generated bitfield helper struct

[software-dov]

I have a bindgen cli question regarding structs that have bitfields.

Let's say I have a C struct that uses bitfields, e.g.

struct my_struct {
    uint8_t priority : 4;
    uint8_t remaining : 3;
    uint8_t success : 1;
} __attribute__((packed));

The generated rust code defines a helper struct that looks like this:

#[repr(C)]
#[derive(Copy, Clone, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct __BindgenBitfieldUnit<Storage> {
    storage: Storage,
}

Is there any way to add custom derives to the helper struct? Adding __BindgenBitfieldUnit to with-derive-custom-struct doesn't seem to do anything, no matter how I tweak the regex to describe the template.
I would absolutely believe that this is not possible, in which case I would stick with a manually defined struct definition in rust.