Included release instructions and general build instructions

.gitignore

@@ -20,3 +20,6 @@ Desktop.ini
 
 # Test artifacts
 /tests/tmp/
+
+# Release artifacts
+release-artifacts/

README.md

@@ -31,6 +31,9 @@ This installs `arduino-cli` and the `arduino:avr` core. If something is
 already installed, Anvil skips it. Run `anvil doctor` at any time to
 check your environment.
 
+If there is no pre-built binary for your platform, or you want to hack on
+Anvil itself, see [Building from Source](#building-from-source) below.
+
 ### Create a project
 
 ```bash
@@ -360,14 +363,72 @@ vid_pid = "0403:6001"
 
 ## Building from Source
 
+If you want to build Anvil yourself -- either because there is no pre-built
+binary for your platform, or because you want to contribute -- here is what
+you need.
+
+### Prerequisites
+
+Anvil is written in Rust and compiles to a single static binary. You need:
+
+- **Rust toolchain** (stable, 2021 edition or later)
+- **A C linker** (`gcc` or equivalent -- Rust uses it under the hood)
+- **MinGW** (only if cross-compiling a Windows binary from Linux)
+- **zip** (only for packaging release artifacts)
+
+### Linux / WSL from scratch
+
+A fresh Ubuntu or WSL instance needs three commands:
+
 ```bash
+# 1. System packages (C linker + cross-compile + packaging tools)
+sudo apt update && sudo apt install build-essential mingw-w64 zip
+
+# 2. Rust toolchain
+curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
+source ~/.cargo/env
+
+# 3. Build
 cargo build --release
 ```
 
-Binary at `target/release/anvil` (Linux) or `target\release\anvil.exe`
-(Windows). Requires Rust 2021 edition.
+The release binary lands at `target/release/anvil`. Copy it somewhere in
+your PATH.
 
-The test suite:
+### Windows (native)
+
+Install Rust from [rustup.rs](https://rustup.rs), which includes the MSVC
+toolchain. Then:
+
+```
+cargo build --release
+```
+
+The binary lands at `target\release\anvil.exe`.
+
+### Release builds (Linux + Windows from one machine)
+
+The `build-release.sh` script at the repo root builds optimized, stripped
+binaries for both platforms and packages them into tarballs and zips:
+
+```bash
+./build-release.sh              # uses git describe for version
+./build-release.sh v1.2.0       # explicit version tag
+```
+
+This produces a `release-artifacts/` directory with:
+
+```
+anvil-v1.2.0-linux-x86_64.tar.gz
+anvil-v1.2.0-linux-x86_64.zip
+anvil-v1.2.0-windows-x86_64.zip
+SHA256SUMS
+```
+
+Upload these to a Gitea release. The script requires `build-essential`,
+`mingw-w64`, and `zip` as described above.
+
+### Running the test suite
 
 ```bash
 cargo test