Rename travis-ci/ directory to ci/

We are no longer using Travis. As such, we should move away from a lot
of CI functionality located in a folder called travis-ci/. This change
renames the travis-ci/ directory to the more generic ci/.
To preserve backwards compatibility until all "consumers" have
transitioned, we add a symbolic link called travis-ci back. It will be
removed in the near term future.

Signed-off-by: Daniel Müller <deso@posteo.net>

ci/rootfs/s390x-self-hosted-builder/actions-runner-libbpf.Dockerfile

@@ -0,0 +1,50 @@
+# Self-Hosted IBM Z Github Actions Runner.
+
+# Temporary image: amd64 dependencies.
+FROM amd64/ubuntu:20.04 as ld-prefix
+ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && apt-get -y install ca-certificates libicu66 libssl1.1
+
+# Main image.
+FROM s390x/ubuntu:20.04
+
+# Packages for libbpf testing that are not installed by .github/actions/setup.
+ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && apt-get -y install \
+        bc \
+        bison \
+        cmake \
+        cpu-checker \
+        curl \
+        flex \
+        git \
+        jq \
+        linux-image-generic \
+        qemu-system-s390x \
+        rsync \
+        software-properties-common \
+        sudo \
+        tree
+
+# amd64 dependencies.
+COPY --from=ld-prefix / /usr/x86_64-linux-gnu/
+RUN ln -fs ../lib/x86_64-linux-gnu/ld-linux-x86-64.so.2 /usr/x86_64-linux-gnu/lib64/
+RUN ln -fs /etc/resolv.conf /usr/x86_64-linux-gnu/etc/
+ENV QEMU_LD_PREFIX=/usr/x86_64-linux-gnu
+
+# amd64 Github Actions Runner.
+ARG version=2.285.0
+RUN useradd -m actions-runner
+RUN echo "actions-runner ALL=(ALL) NOPASSWD: ALL" >>/etc/sudoers
+RUN echo "Defaults env_keep += \"DEBIAN_FRONTEND\"" >>/etc/sudoers
+RUN usermod -a -G kvm actions-runner
+USER actions-runner
+ENV USER=actions-runner
+WORKDIR /home/actions-runner
+RUN curl -L https://github.com/actions/runner/releases/download/v${version}/actions-runner-linux-x64-${version}.tar.gz | tar -xz
+VOLUME /home/actions-runner
+
+# Scripts.
+COPY fs/ /
+ENTRYPOINT ["/usr/bin/entrypoint"]
+CMD ["/usr/bin/actions-runner"]