build error in Windows.

I received the following error.
```
Compiling mruby3-sys v3.2.0
error[E0587]: type has conflicting packed and align representation hints
--> C:\private\SRCs\Rust2\mruby3-sys_sample1\target\debug\build\mruby3-sys-3256b2c0dc686794\out/bindings.rs:4418:1
|
4418 | pub union __mingw_ldbl_type_t {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For more information about this error, try `rustc --explain E0587`.
error: could not compile `mruby3-sys` (lib) due to previous error

```
- Windows11 64bit
- mingw64 rust
- native rust

I believe this error is caused by bindgen, can I ask you to take care of it,
e.g. change the version of bindgen used by mruby3-sys?

Start with the generated target/debug/build/mruby3-sys-3256b2c0dc686794/out/bindings.rs at the __mingw_ldbl_type_t definition, then inspect how mruby3-sys invokes bindgen. Reproduce the Windows 11 mingw64 build and verify that the E0587 conflicting packed and align representation error no longer occurs.

Written by the indexing model from the issue text.