Fails to build on x86_64-pc-msys

I see a similar error to #6, but different arch and different types so i opened a separate issue.

on gcc x86_64-pc-msys 11.3

```
# github.com/pjbgf/sha1cd/cgo
..\..\..\go\pkg\mod\github.com\pjbgf\sha1cd@v0.2.2\cgo\sha1_windows.go:19:31: cannot use (_Ctype_ulonglong)(len(p)) (value of type _Ctype_ulonglong) as type _Ctype_ulong in variable declaration
```