Update how-to-build-toolchain.md for the latest swiftwasm-build layout

Author: kateinoigakukun

src/contribution-guide/how-to-build-toolchain.md

@@ -1,32 +1,30 @@
 # How to build toolchain
 
 This document describes how to build the toolchain for WebAssembly.
-This is just a quick guide, so if you want to know more about the toolchain, it might be good entry point to read [continuous integration scripts](https://github.com/swiftwasm/swift/blob/swiftwasm/.github/workflows/build-toolchain.yml).
+This is just a quick guide, so if you want to know more about the toolchain, it might be good entry point to read [continuous integration scripts](https://github.com/swiftwasm/swiftwasm-build/blob/main/.github/workflows/build-toolchain.yml).
 Or you can ask questions in GitHub issues or SwiftWasm Discord server (see [the official website](https://swiftwasm.org) for the link).
 
 ## 1. Checkout the project source code.
 
 ```sh
 $ mkdir swiftwasm-source
 $ cd swiftwasm-source
-$ git clone https://github.com/swiftwasm/swift.git
-$ ./swift/utils/update-checkout --clone --scheme wasm
+$ git clone https://github.com/swiftwasm/swiftwasm-build.git
+$ cd swiftwasm-build
+$ ./tools/build/install-build-sdk.sh main
+$ ./tools/git-swift-workspace --scheme main
 ```
 
 ## 2. Install required dependencies
 
 1. [Please follow the upstream instruction](https://github.com/apple/swift/blob/main/docs/HowToGuides/GettingStarted.md#installing-dependencies)
-2. Download WebAssembly specific build toolchain
-
-```sh
-$ ./swift/utils/webassembly/install-build-sdk.sh
-```
-
-3. (If you want to run test suite) Install [`Wasmer`](https://wasmer.io/)
+2. (If you want to run test suite) Install [`Wasmtime`](https://wasmtime.dev/)
 
 ## 3. Build the toolchain
 
-`./swift/utils/webassembly/build-toolchain.sh` will build:
+`./tools/build/build-toolchain.sh`
+
+This script will build the following components:
 
 1. Swift compiler that can compile Swift code to WebAssembly support
 2. Swift standard library and core libraries for WebAssembly
@@ -35,16 +33,17 @@ $ ./swift/utils/webassembly/install-build-sdk.sh
 ## Build on Docker
 
 You can also build the toolchain on Docker image used in CI.
+Note that you have already checked out the source code in [the previous step](#1-checkout-the-project-source-code).
 
 ```sh
 $ docker volume create oss-swift-package
 $ docker run --name swiftwasm-ci-buildbot \
     -dit \
     -w /home/build-user/ \
-    -v $PWD/swift:/home/build-user/swift \
+    -v ./swiftwasm-source:/source \
     -v oss-swift-package:/home/build-user \
     ghcr.io/swiftwasm/swift-ci:main-ubuntu-20.04
-$ docker exec swiftwasm-ci-buildbot ./swift/utils/webassembly/ci.sh
+$ docker exec swiftwasm-ci-buildbot /bin/bash -lc 'env; cp -r /source/* /home/build-user/; ./swiftwasm-build/tools/build/ci.sh main'
 $ docker cp swiftwasm-ci-buildbot:/home/build-user/swift-wasm-DEVELOPMENT-SNAPSHOT-*-ubuntu-20.04.tar.gz .
 ```