Building `aws-lc-rs` with FIPS enabled on Windows ARM64 fails due to x64/ARM64 toolchain mismatch during native CMake build.

[sfc-gh-fpawlowski]

Problem:

Building aws-lc-rs with FIPS enabled on Windows ARM64 fails due to x64/ARM64
toolchain mismatch during native CMake build.

In our CI (windows-11-arm runner), we target aarch64-pc-windows-msvc and
call vcvarsall.bat arm64 before cargo build.
However, the aws-lc-fips-sys build path appears to override this by invoking
vcvarsall.bat x64 via its Windows helper script, which results in x64
libraries being selected in the FIPS CMake subprocess and causes linker failure:

library machine type 'x64' conflicts with target machine type 'ARM64'

Non-FIPS builds (via aws-lc-sys) work on the same runner/target; the failure
is specific to the FIPS path (aws-lc-fips-sys).

Relevant details

AWS-LC for Rust versions or commit:

• aws-lc-rs = 1.16.1
• aws-lc-fips-sys = 0.13.12
• cmake = 0.1.54

System information:

• CPU architecture: ARM64 (aarch64)
• CPU name: GitHub-hosted Windows ARM runner (windows-11-arm)
• OS: Windows 11 ARM (GitHub Actions hosted image)

Verified reproduction

In snowflakedb/universal-driver PR #427
on windows-11-arm, building sf_core with --all-features (which enables
rustls/fips → aws-lc-fips-sys) targeting aarch64-pc-windows-msvc fails
with LNK1112 x64 vs ARM64 conflict.

• PR: ci: enable --all-features on ARM64 to reproduce FIPS linker failure snowflakedb/universal-driver#427
• Job: https://github.com/snowflakedb/universal-driver/actions/runs/22779459689/job/66081199710

Likely minimal reproducer (not yet validated end-to-end)

Cargo.toml:

[package]
name = "fips-arm64-repro"
edition = "2021"

[dependencies]
aws-lc-rs = { version = "1.16", features = ["fips"] }

src/main.rs:

fn main() {
    aws_lc_rs::init();
    println!("aws-lc-rs FIPS loaded");
}

Steps:

1. Use a Windows ARM64 machine (observed on GitHub Actions windows-11-arm;
   may also reproduce with x64 host cross-compiling to ARM64 target).
2. Set up ARM64 MSVC environment:

   call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsall.bat" arm64
   

3. Install target: rustup target add aarch64-pc-windows-msvc
4. Build:

   cargo build --target aarch64-pc-windows-msvc
   

5. Expected: linker error with x64 vs ARM64 machine type conflict.

Observed behavior in source/build path:

• aws-lc-fips-sys/builder/printenv.bat (lines 30-37) calls vcvarsall.bat x64.
• aws-lc-fips-sys/builder/cmake_builder.rs (lines 273-281) imports env from
  that script for Windows builds via collect_vcvarsall_bat().
• This overrides the caller's ARM64 env (vcvarsall arm64) for the FIPS CMake
  build path.
• The non-FIPS path (aws-lc-sys/builder/cmake_builder.rs lines 305-324) has
  explicit ARM64 Windows handling and works correctly.

Expected behavior:

• When target is aarch64-pc-windows-msvc, FIPS build should respect the
  target architecture and produce ARM64-compatible artifacts, consistent with
  how aws-lc-sys (non-FIPS) handles it.

Build log (from CI run above):

error: failed to run custom build command for `aws-lc-fips-sys v0.13.12`
...
link : fatal error LNK1112: module machine type 'x64' conflicts with target machine type 'ARM64'