Restore Windows ARM64 case builds when static CRT linking cannot locate psapi

[LunaStev]

Observed on PR #606 head 037baf248a9793be2b0563fb28972b5c4fb9714a (2026-09-12).

The Cases Windows GNU arm64 job now fails while building the native Rust compiler, before any Wave case runs.

Failing cases job:

error: could not find native static library `psapi`, perhaps an -L flag is missing?
error: could not compile `llvm-sys` (lib) due to 1 previous error

The failing command is:

cargo build --locked --release --no-default-features --features llvm-target-aarch64 --jobs 2

The same PR's native ARM64 build job successfully builds the compiler and passes the LLVM allocator regression. Its build command includes --target aarch64-pc-windows-msvc. The cases job also installs llvm-mingw and changes PATH. These are investigation leads, not a proven explanation.

Both logs show:

• RUSTFLAGS: -C target-feature=+crt-static -l bcrypt -l ws2_32
• LIB containing provisioned ARM64 libxml2, MSVC ARM64, Windows SDK UCRT ARM64, and Windows SDK UM ARM64 directories.
• LLVM 21.1.8 and a native ARM64 Rust host.

Starting points:

• cases workflow provisioning and build
• static CRT/libxml2 provisioning
• working native build workflow

Acceptance:

• Capture cargo -vv/llvm-sys link-search output and verify the actual ARM64 SDK psapi.lib resolution.
• Reconcile native target selection, SDK library search paths, and any PATH interaction; preserve the configured output path or update all consumers if an explicit Cargo target changes it.
• Keep Rust, LLVM, and libxml2 in the compatible static-CRT allocator domain established for Investigate native Windows ARM64 access violations across Wave cases #493. Do not revert to the crashing allocation/free combination or mix x64 libraries into ARM64.
• Native ARM64 compiler architecture verification and the case runner must execute after the build succeeds.
• Review the analogous release workflow for the same setup pattern.

Related: #493, #292, #606. This is a compiler-build/link dependency failure, not evidence that generated GNU ARM64 programs failed.