ci: use chainguard latest image when building in CI

So that we can run CI without having access to the Elastic docker
registry.

Author: xrmx

.github/workflows/ci.yml

@@ -48,13 +48,7 @@ jobs:
     - run: python -m build
     - name: Set up Docker Buildx
       uses: docker/setup-buildx-action@6524bf65af31da8d45b59e8c27de4bd072b392f5 # v3.8.0
-    - name: Log in to the Elastic Container registry
-      uses: docker/login-action@9780b0c442fbb1117ed29e0efdff1e18412f7567 # v3.3.0
-      with:
-        registry: ${{ secrets.ELASTIC_DOCKER_REGISTRY }}
-        username: ${{ secrets.ELASTIC_DOCKER_USERNAME }}
-        password: ${{ secrets.ELASTIC_DOCKER_PASSWORD }}
-    - run: docker build -f operator/Dockerfile --build-arg DISTRO_DIR=./dist .
+    - run: docker build -f operator/Dockerfile --build-arg PYTHON_GLIBC_IMAGE=cgr.dev/chainguard/python --build-arg PYTHON_GLIBC_IMAGE_VERSION=latest --build-arg DISTRO_DIR=./dist --build-arg IMAGE=cgr.dev/chainguard/busybox --build-arg IMAGE_VERSION=latest .
 
   test:
     runs-on: ubuntu-latest

operator/Dockerfile

@@ -1,4 +1,7 @@
-FROM docker.elastic.co/wolfi/python:3.12-dev@sha256:2f10787cc037b197f6a5d1a031c31706ae59642708c8b3b5ddfd3fa79605e9ad AS build
+ARG PYTHON_GLIBC_IMAGE="docker.elastic.co/wolfi/python"
+ARG PYTHON_GLIBC_IMAGE_VERSION="3.12-dev@sha256:2f10787cc037b197f6a5d1a031c31706ae59642708c8b3b5ddfd3fa79605e9ad"
+
+FROM ${PYTHON_GLIBC_IMAGE}:${PYTHON_GLIBC_IMAGE_VERSION} AS build
 
 ENV LANG=C.UTF-8
 ENV PYTHONDONTWRITEBYTECODE=1
@@ -32,7 +35,10 @@ RUN apk add gcc g++ python3-dev musl-dev linux-headers
 
 RUN pip install --no-cache-dir --target workspace /opt/distro/*.whl -r requirements.txt
 
-FROM docker.elastic.co/wolfi/chainguard-base:latest@sha256:26caa6beaee2bbf739a82e91a35173892dfe888d0a744b9e46cdc19a90d8656f
+ARG IMAGE="docker.elastic.co/wolfi/chainguard-base"
+ARG IMAGE_VERSION="latest@sha256:26caa6beaee2bbf739a82e91a35173892dfe888d0a744b9e46cdc19a90d8656f"
+
+FROM ${IMAGE}:${IMAGE_VERSION}
 
 COPY --from=build /operator-build/workspace /autoinstrumentation
 COPY --from=build-musl /operator-build/workspace /autoinstrumentation-musl