fix(vortex-duckdb): make build.rs cross-platform for Windows

[joseph-isaacs]

What

Makes vortex-duckdb's build.rs build on Windows (x86_64-pc-windows-msvc and aarch64-pc-windows-msvc). Today it is unix-only, so the duckdb-vortex DuckDB extension can't be built for Windows — the build fails with error[E0433]: failed to resolve: could not find unixinos``.

Changes (all in vortex-duckdb/build.rs)

• Symlink: drop the unconditional use std::os::unix::fs::symlink. The crate_dir/duckdb symlink is only a dev/tooling convenience — the build uses the extracted inner_dir directly — so it now lives in a #[cfg(unix)] helper that is a no-op on other platforms.
• Prebuilt libraries: add x86_64-pc-windows-msvc → windows/amd64 and aarch64-pc-windows-msvc → windows/arm64 to the download match (DuckDB ships libduckdb-windows-amd64.zip / libduckdb-windows-arm64.zip), and recognise duckdb.dll as a build artifact.
• C++ compile flags: gate the GCC/Clang -Wall -Wextra -Wpedantic -Werror / -isystem flags behind a non-MSVC check; on MSVC use /W4 + a normal include (cl rejects the GNU-style flags).
• rpath: skip the -Wl,-rpath link arg on Windows (MSVC's linker rejects it; the DLL is resolved via PATH instead).

Platform conditionals read CARGO_CFG_TARGET_OS / CARGO_CFG_TARGET_ENV (the build target) rather than cfg!(), which in a build script reflects the host.

Context / why now

The duckdb-vortex repo is enabling Windows CI. windows_amd64 got as far as compiling before hitting this build script; windows_arm64 previously also hit an aws-lc-sys ARM64 assembly link failure (LNK1181), but that no longer applies on current develop — the TLS stack resolves to rustls + ring (ring v0.17), not aws-lc-rs.

Testing

Formatting + type review done locally; -W/rpath/MSVC branches are runtime conditionals that compile on every host (only the trivial symlink helper is cfg-gated). The authoritative Windows build is this PR's CI. Opened as a draft for that reason — once green, duckdb-vortex can bump its vortex submodule and opt the windows_* archs back into its matrix.

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

⚡ 1 improved benchmark
❌ 1 regressed benchmark
✅ 1273 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	chunked_varbinview_canonical_into[(1000, 10)]	162.1 µs	198 µs	-18.12%
⚡	Simulation	chunked_varbinview_canonical_into[(100, 100)]	309.2 µs	273.2 µs	+13.16%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing feat/windows-arm64-build (4cd6b6b) with develop (326b475)}