Add focal

ci_container/Dockerfile.focal

@@ -0,0 +1,40 @@
+FROM docker.io/library/ubuntu:focal
+
+LABEL org.opencontainers.image.created=${BUILDTIMESTAMP} \
+      org.opencontainers.image.authors="Heiko Reese <reese@kit.edu>" \
+      org.opencontainers.image.title="exim build container" \
+      org.opencontainers.image.description="A buld environment for exim-encrypt-dlfunc" \
+      org.opencontainers.image.source="https://git.scc.kit.edu/mail/exim-encrypt-dlfunc/" \
+      org.opencontainers.image.licenses="Apache-2.0"
+
+
+RUN apt-get update; \
+    DEBIAN_FRONTEND=noninteractive DEBIAN_PRIORITY=critical apt-get install --no-install-recommends -y \
+        build-essential \
+        exim4-daemon-heavy \
+        exim4-dev \
+        gcovr \
+        git \
+        libsodium-dev \
+        openssl \
+        pkg-config \
+        python3-pip \
+        libxml2-utils \
+        debhelper \
+        debsigs \
+        devscripts \
+        dh-make \
+        git-buildpackage \
+        gpgv1 \
+        meson \
+        less \
+        mc \
+        openssh-client \
+        vim; \
+    DEBIAN_FRONTEND=noninteractive DEBIAN_PRIORITY=critical apt-get clean; \
+    rm -rf /var/lib/apt/lists/*;
+
+RUN pip3 install --upgrade meson ninja; \
+    rm -rf ~/.cache/pip/*;
+
+WORKDIR /mnt/