Small tweaks to the install instructions (#94)

* Small tweaks to the install instructions

* Typo

Author: elliottt

README.md

@@ -24,7 +24,7 @@ To build from source, you need to ensure that the headers and object files for t
 
 Alternatively, the engine can also be built from source using `c-dependencies/spidermonkey/build-engine.sh`. That should only be required if you want to modify the engine itself, however.
 
-In additon you need to have the following tools installed to successfully build, and build from a linux based system.
+In addition you need to have the following tools installed to successfully build, and build from a linux based system.
 
 - Rust 
   ```
@@ -43,21 +43,25 @@ In additon you need to have the following tools installed to successfully build,
   ```sh
   rustup target add wasm32-wasi
   ```
-- cbindgen
+- [cbindgen](https://github.com/eqrion/cbindgen#quick-start)
   ```sh
   cargo install cbindgen
   ```
-- wasi-sdk
+- [wasi-sdk, version 12](https://github.com/WebAssembly/wasi-sdk/releases/tag/wasi-sdk-12),
+  with alternate [install instructions](https://github.com/WebAssembly/wasi-sdk#install)
   ```sh
   curl -sS -L -O https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-12/wasi-sdk-12.0-linux.tar.gz
   tar xf wasi-sdk-12.0-linux.tar.gz
   sudo mkdir -p /opt/wasi-sdk
   sudo mv wasi-sdk-12.0/* /opt/wasi-sdk/
   ```
+
 - rust version - the rust version may need to be pinned due to the WASI spidermonkey version, the current version can be found at [main.yml](.github/workflows/main.yml) under "Install pinned Rust version and wasm32-wasi target"
   ```
    rustup update 1.57.0 --no-self-update
-   rustup default 1.57.0
+
+   cd /location/of/js-compute-runtime
+   rustup override set 1.57.0
   ```
 
 Once that is done, the runtime and the CLI tool for applying it to JS source code can be built using cargo: