Document Windows build tools setup

README.md

@@ -15,7 +15,18 @@ RustToolChain.jl is a Julia package that provides Rust toolchains (especially `c
 
 - **Linux**: x86_64 (glibc, musl), aarch64 (glibc, musl), i686 (glibc, musl)
 - **macOS**: x86_64, aarch64
-- **Windows**: x86_64, aarch64
+- **Windows**: x86_64
+
+### Preparation (Windows users only)
+
+Windows users need to run the following in an Administrator PowerShell to install the required build tools:
+
+```ps
+winget install -e --id Microsoft.VisualStudio.2022.BuildTools `
+  --accept-source-agreements `
+  --accept-package-agreements `
+  --override "--wait --passive --add Microsoft.VisualStudio.Workload.VCTools --includeRecommended"
+```
 
 ## Installation
 
@@ -87,9 +98,12 @@ run(`$(cargo()) build --release`)
 
 This package uses Julia's Artifacts system to automatically download and manage Rust toolchains on Unix-like platforms. On first use, the appropriate Rust toolchain for your platform will be automatically downloaded.
 
+The `cargo()` and `rustc()` functions return commands that use the isolated Windows toolchain when no system `cargo` or `rustc` is available.
+
+### Note for Windows Users
+
 Windows uses a different installation path. Instead of installing the large Rust distribution tarball through Julia Artifacts, RustToolChain.jl downloads `rustup-init.exe` from `https://win.rustup.rs` and installs the Rust version recorded in `Artifacts.toml` with `rustup toolchain install --profile default`. The installation is isolated under this package's Julia scratchspace by setting package-local `RUSTUP_HOME` and `CARGO_HOME` directories. It does not modify the user's `PATH` or the user's existing Rust installation.
 
-The `cargo()` and `rustc()` functions return commands that use the isolated Windows toolchain when no system `cargo` or `rustc` is available.
 
 ## Development