[libc] Add docker container for llvm-libc buildbot worker.

Summary: Created a docker container to provide transparency and easy changes to the llvm-libc buildbot intfra.

Reviewers: sivachandra

Reviewed By: sivachandra

Subscribers: MaskRay, tschuett, libc-commits

Tags: #libc-project

Differential Revision: https://reviews.llvm.org/D75596

libc/utils/buildbot/Dockerfile

@@ -0,0 +1,34 @@
+FROM debian:10
+
+# Installing dependecies.
+RUN dpkg --add-architecture i386
+RUN apt-get update
+RUN apt-get install -y build-essential clang subversion git vim \
+  zip libstdc++6:i386 file binutils-dev binutils-gold cmake python-pip \
+  ninja-build
+RUN python -m pip install buildbot-slave==0.8.12
+
+# Change linker to gold.
+RUN update-alternatives --install "/usr/bin/ld" "ld" "/usr/bin/ld.gold" 20
+
+# Create and switch to buildbot user.
+RUN useradd buildbot --create-home
+USER buildbot
+
+WORKDIR /home/buildbot
+
+# Use clang as the compiler.
+ENV CC=/usr/bin/clang
+ENV CXX=/usr/bin/clang++
+
+ENV WORKER_NAME="libc-x86_64-debian"
+
+# Set up buildbot host and maintainer info.
+RUN mkdir -p "${WORKER_NAME}/info/"
+RUN bash -c "(uname -a ; \
+  gcc --version | head -n1 ; ld --version \
+  | head -n1 ; cmake --version | head -n1 ) > ${WORKER_NAME}/info/host"
+RUN echo "Paula Toth <paulatoth@google.com>" > "${WORKER_NAME}/info/admin"
+
+ADD --chown=buildbot:buildbot run.sh .
+ENTRYPOINT ["./run.sh"]

libc/utils/buildbot/README.txt

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+This folder contains resources needed to create a docker container for
+llvm-libc builbot worker.
+
+Dockerfile: Sets up the docker image with all pre-requisites.
+
+run.sh: Script to create and start buildbot worker with supplied password.
+
+cmd to build the docker container:
+```
+docker build -t llvm-libc-buildbot-worker .
+```
+
+cmd to run the buildbot:
+```
+docker run -it llvm-libc-buildbot-worker <passwd>
+```

libc/utils/buildbot/run.sh

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+#!/bin/bash
+
+# This serves as the entrypoint for docker to allow us to
+# run and start the buildbot while supplying the password
+# as an argument.
+buildslave create-slave --keepalive=200 "${WORKER_NAME}" \
+  lab.llvm.org:9990 "${WORKER_NAME}" "$1"
+
+buildslave start "${WORKER_NAME}"
+tail -f ${WORKER_NAME}/twistd.log