Drop add-on building support.

Author: mrstegeman

.github/workflows/build-all.yml

@@ -1,36 +1,4 @@
 # Add-on builder
 
-Add-on builder for the WebThings Gateway.
-
-This repository will build addons for macOS, Linux, and Raspberry Pi variants
-of the gateway.
-
-Use the `trigger-build.py` script to initiate a build. Modifying
-any of the files in this repository and pushing them will also
-trigger a build of all of the adapters.
-
-# `trigger-build.py`
-
-The `trigger-build.py` will trigger a GitHub workflow to start
-building an image. You can check the progress by watching
-https://github.com/WebThingsIO/addon-builder/actions
-
-If you only want to build for one adapter, you can pass that adapter on
-the command line.
-```
-./trigger-build.py --token <your-token> gpio-adapter:node
-```
-
-# Deployed tarballs
-
-The tarballs that are built will be deployed to mozilla-gateway-addons AWS bucket.
-URLs to the addons will be printed at the end of the job. You can
-also view all of the addons by using:
-```
-aws s3 ls s3://mozilla-gateway-addons/
-```
-or
-```
-aws s3 ls s3://mozilla-gateway-addons/builder/
-```
-to view the addons which have been built (but not yet deployed).
+This repository contains (and builds) a set of toolchains for cross-compiling
+Python and NodeJS add-ons for WebThings Gateway.