ci: fix ninja-build on EL9 workers; drop runner-hosted Buildbot workflow

On Enterprise Linux 9 ninja-build lives in EPEL and is built against the
CRB (CodeReady Builder) repo, so both must be enabled before it resolves.
The rocky image pulled in epel-release but never enabled CRB, and the ubi
image had neither EPEL nor CRB, so both failed with "Unable to find a
match: ninja-build". Enable dnf-plugins-core + crb on Rocky, and install
the EPEL release RPM plus ubi-9-codeready-builder-rpms on UBI.

Also remove .github/workflows/buildbot-ci.yml, which stood up a Buildbot
master and workers inside a GitHub Actions runner. CI now runs solely
through the real docker-compose deployment, triggered by the GitHub
webhook or an operator's buildbot sendchange. Scrub the now-stale
references to that workflow from the docs and module docstrings; the
PBChangeSource / sendchange / wait_for_builds.py operator path stays.

Author: Aasyaco

.github/workflows/buildbot-ci.yml

@@ -16,14 +16,15 @@ large regression databases.
 
 The `freebsd/freebsd-toolchain:15.1` image is a FreeBSD-kernel image: it only
 builds and runs on a FreeBSD Docker host. Set `BUILDBOT_ACTIVE_WORKERS` to the
-comma-separated subset of workers a given host can serve (the GitHub workflow
-uses `debian,fedora,rocky,ubi`); the full 5-image matrix stays defined.
+comma-separated subset of workers a given host can serve (a Linux Docker host
+serves `debian,fedora,rocky,ubi`); the full 5-image matrix stays defined.
 
-Alongside the GitHub webhook, the master exposes a `PBChangeSource`, so a build
-can be triggered over localhost with `buildbot sendchange`. The `Buildbot-CI`
-GitHub workflow uses this: it stands up a real master plus the four Linux
-latent workers on the runner, injects the current revision over
-`localhost:9989`, and fails unless every active builder finishes successfully.
+Alongside the GitHub webhook, the master exposes a `PBChangeSource`, so an
+operator can trigger a build against the deployed master with
+`buildbot sendchange --master <host>:9989`, without depending on the webhook.
+`buildbot/ci/wait_for_builds.py` polls the REST API and exits non-zero unless
+every active builder finishes successfully, turning such a run into a pass/fail
+gate.
 
 The Debian builder also runs clang-format in verification mode, cppcheck,
 clang-tidy, and scan-build. Formatting never rewrites the checkout. Each

buildbot/README.md

@@ -18,9 +18,9 @@
 def create_change_sources():
     """Use webhooks primarily and pollers as loss/restart recovery.
 
-    A PBChangeSource is also exposed so an operator (or the GitHub Actions
-    workflow) can inject a change over the master PB port with
-    ``buildbot sendchange`` without depending on the GitHub webhook.
+    A PBChangeSource is also exposed so an operator can inject a change over
+    the master PB port with ``buildbot sendchange`` without depending on the
+    GitHub webhook.
     """
     return [
         changes.PBChangeSource(user=CHANGE_USER, passwd=CHANGE_PASSWORD),

buildbot/changesources.py

@@ -2,8 +2,8 @@
 """Wait for the Buildbot builds triggered over localhost to finish.
 
 Polls the master REST API until every expected builder has a completed build,
-then exits non-zero if any of those builds did not succeed. Used by the
-Buildbot-CI GitHub workflow to turn a real Buildbot run into a pass/fail gate.
+then exits non-zero if any of those builds did not succeed. Turns a real
+Buildbot run triggered over the PB port into a pass/fail gate.
 """
 
 import json

buildbot/ci/wait_for_builds.py

@@ -7,7 +7,8 @@ declare -a requested=()
 
 # Usage: build-images.sh [-jN] [name ...]
 # With no names, every image is built. Pass names (e.g. debian fedora rocky ubi)
-# to build a subset -- the Linux-only GitHub workflow uses this to skip freebsd.
+# to build a subset -- a Linux Docker host uses this to skip the freebsd image,
+# which only builds and runs on a FreeBSD Docker host.
 for arg in "$@"; do
     case "${arg}" in
         -j*) parallelism="${arg#-j}" ;;

buildbot/docker/build-images.sh

@@ -1,7 +1,9 @@
 FROM rockylinux/rockylinux:9
 ARG BUILDBOT_WORKER_VERSION=4.2.1
 ENV BUILDBOT_WORKER_VERSION=${BUILDBOT_WORKER_VERSION}
-RUN dnf -y install epel-release && dnf -y groupinstall "Development Tools" && \
+RUN dnf -y install epel-release dnf-plugins-core && \
+    dnf config-manager --set-enabled crb && \
+    dnf -y groupinstall "Development Tools" && \
     dnf -y install bash ca-certificates ccache clang cmake git ninja-build python3 \
     python3-pip tar && dnf clean all
 COPY buildbot/docker/install-worker.sh /usr/local/bin/install-worker

buildbot/docker/workers/rocky.Dockerfile

@@ -1,7 +1,10 @@
 FROM redhat/ubi9:latest
 ARG BUILDBOT_WORKER_VERSION=4.2.1
 ENV BUILDBOT_WORKER_VERSION=${BUILDBOT_WORKER_VERSION}
-RUN dnf -y install bash ca-certificates ccache clang cmake gcc gcc-c++ git make \
+RUN dnf -y install dnf-plugins-core \
+    https://dl.fedoraproject.org/pub/epel/epel-release-latest-9.noarch.rpm && \
+    dnf config-manager --set-enabled ubi-9-codeready-builder-rpms && \
+    dnf -y install bash ca-certificates ccache clang cmake gcc gcc-c++ git make \
     ninja-build python3 python3-pip tar && dnf clean all
 COPY buildbot/docker/install-worker.sh /usr/local/bin/install-worker
 RUN /usr/local/bin/install-worker