Windows-rs: Support architecture-specific builds

[ZCWorks]

in ver.0.11.0: Windows::Win32::UI::Shell::NOTIFYICONDATAW is "#[repr(C, packed(1))]" so Shell_NotifyIconW fails

in ver.0.10.0: it is "#[repr(C)]", Shell_NotifyIconW goes OK

[tim-weis]

The issue can be reproduced using the following:

Cargo.toml:

[package]
name = "shell_test"
version = "0.0.0"
edition = "2018"

[dependencies]
windows = "0.11.0"

[build-dependencies]
windows = "0.11.0"

build.rs:

fn main() {
    windows::build!(
        Windows::Win32::UI::Shell::NOTIFYICONDATAW,
    );
}

main.rs:

mod bindings {
    windows::include_bindings!();
}

fn main() {}

• cargo build --target i686-pc-windows-msvc produces the 32-bit bindings
• cargo build --target x86_64-pc-windows-msvc produces the 64-bit bindings

According to the Windows SDK headers, the NOTIFIYICONDATAW structure should be packed(1), unless the target architecture is _WIN64 (not sure whether that includes ARM64).

The metadata contains type definitions for both byte-packed and natural type layout, presumably gated on the SupportedArchitecture attribute (which ILSpy won't display, though it should), but those don't translate into the generated bindings.

[weltkante]

unless the target architecture is _WIN64 (not sure whether that includes ARM64).

ARM64 sets _WIN64 - doc says:

_WIN64 Defined as 1 when the compilation target is 64-bit ARM or x64. Otherwise, undefined.

[kennykerr]

The metadata now includes arch-specific struct definitions, but the Windows crate doesn't yet sniff out the target for the build and generate the appropriate definitions.