CI: Disable the CI Build on push to master branch

[lupyuen]

Summary

Due to the recent cost-cutting, we are no longer running PR Merge Jobs in the nuttx and nuttx-apps repos. For this to happen, I am now running a script on my computer that will cancel any PR Merge Jobs that appear: kill-push-master.sh

This PR disables PR Merge Jobs permanently, so that we no longer need to run the script. This prevents our CI Charges from over-running, in case the script fails to operate properly.

Impact

Some NuttX Developers may wish to run the PR Merge Jobs in their repos. They will have to re-enable the job in build.yml:

on: ...
  push: ...
    branches:
      - master

Or they may rename the Default Branch from master to releases/master branch. Which will continue to execute PR Merge Jobs:

No Impact when Creating / Updating a PR: They will still undergo the same CI Checks.

No Impact to Release Branch: Merging a PR to the Release Branch will still run the PR Merge Job (exactly like today). This ensures that the Release Branch will be verified through complete CI Checks.

No Impact to Docker Builds: When the Dockerfile is updated, it will trigger the CI Workflow docker_linux.yml. Which is not affected by this PR, and will continue to run (exactly like today).

No Impact to Documentation: When the docs are updated, they are published to NuttX Website via the CI Workflow main.yml from the nuttx-website repo (scheduled daily). Which is not affected by this PR, and will continue to run (exactly like today).

Testing

Creating a PR will trigger the CI Checks: (exactly like today)

• https://github.com/lupyuen5/label-nuttx/actions/runs/11652645194?pr=88

Merging a PR will no longer execute the "Merge Pull Request" job:

• https://github.com/lupyuen5/label-nuttx/actions/workflows/build.yml

If we create a branch releases/master and merge a PR: CI Checks shall still execute:

• https://github.com/lupyuen5/label-nuttx/actions/runs/11654331888