doc: document approach for building wasm in deps

Refs: nodejs/security-wg#1236

Signed-off-by: Michael Dawson <midawson@redhat.com>
PR-URL: nodejs#55940
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: mhdawson

doc/contributing/maintaining/maintaining-dependencies.md

@@ -145,6 +145,48 @@ can be added as a non-externalizable dependency. In this case
 simply add the path to the JavaScript file in the `deps_files`
 list in the `node.gyp` file.
 
+## Common approach for dependencies with WASM components
+
+WASM components within dependencies are most often built
+outside of the regular Node.js `make build` step. They also
+require different tools.
+
+It is important that the tools and their versions used to build
+WASM components shipped within Node.js are well documented and
+be available if needed to rebuild/update older Node.js versions.
+
+In order to minimize the different number of tools and versions
+used to build WASM components and to document and ensure future
+availability, the project builds and maintains a common
+[wasm-builder](https://github.com/nodejs/wasm-builder) container
+that should be use to build WASM components in Node.js
+dependencies.
+
+The container provides a durable copy of the versions of the tools
+used for a specific build which are under the control of the Node.js
+project. In addition, the tools and verions are documented through metadata
+within the container in the `/home/node/metadata directory`.
+
+The available tools can be found by looking at the current version of the
+[Dockerfile](https://github.com/nodejs/wasm-builder/blob/main/container-build-info/Dockerfile)
+used to create the container.
+
+If additional WASM tool are needed beyond those available in the
+container, additions should be PR'd into the wasm-builder container.
+
+Examples of using the container include:
+
+* [build/wasm.js](https://github.com/nodejs/undici/blob/main/build/wasm.js) from undici
+* [tools/build-wasm.js](https://github.com/nodejs/amaro/blob/main/tools/build-wasm.js) from amaro
+
+In addition to using the container to build WASM components, the goal is also
+for the WASM components and final files that are shipped with Node.js to be
+built by the [dep-updaters](https://github.com/nodejs/node/tree/main/tools/dep_updaters)
+that are run on a regular basis and that they use only the files available in the Node.js
+repo for the dependency. For example, being able to rebuild the WASM and files that
+we ship in Node.js using only the files in
+[../deps/undici](https://github.com/nodejs/node/tree/main/deps/undici).
+
 ## Updating dependencies
 
 Most dependencies are automatically updated by