Add Dockerfile for CI.

This makes ykllvm build with the new docker infrastructure.

Author: vext01

.buildbot_dockerfile_debian

@@ -0,0 +1,9 @@
+FROM debian:bullseye
+ARG CI_UID
+RUN useradd -m -u ${CI_UID} ci
+RUN apt-get update && \
+    apt-get -y install build-essential curl cmake python3-distutils git
+WORKDIR /ci
+RUN chown ${CI_UID}:${CI_UID} .
+COPY --chown=${CI_UID}:${CI_UID} . .
+CMD sh -x .buildbot.sh