build: Update AppImage Dockerfile to Ubuntu 20.04

to get newer openssl required for cryptography

pyca/cryptography#8449

we also add `g++` here because the `zxing-cpp` build needs it.

Author: EchterAgo

contrib/build-linux/appimage/Dockerfile_ub1804

@@ -0,0 +1,63 @@
+FROM ubuntu:20.04@sha256:3246518d9735254519e1b2ff35f95686e4a5011c90c85344c1f38df7bae9dd37
+
+ARG UBUNTU_MIRROR=http://archive.ubuntu.com/ubuntu/
+
+ENV LC_ALL=C.UTF-8 LANG=C.UTF-8
+
+ENV UBUNTUDIST=focal
+
+# This prevents questions during package installations
+ENV DEBIAN_FRONTEND=noninteractive
+
+# If a package version does not exist anymore you can use "apt-cache policy <pkg>" to display the available versions
+RUN echo deb ${UBUNTU_MIRROR} ${UBUNTUDIST} main restricted universe multiverse > /etc/apt/sources.list && \
+    echo deb ${UBUNTU_MIRROR} ${UBUNTUDIST}-updates main restricted universe multiverse >> /etc/apt/sources.list && \
+    echo deb ${UBUNTU_MIRROR} ${UBUNTUDIST}-backports main restricted universe multiverse >> /etc/apt/sources.list && \
+    echo deb ${UBUNTU_MIRROR} ${UBUNTUDIST}-security main restricted universe multiverse >> /etc/apt/sources.list && \
+    apt-get update -q && \
+    apt-get install -qy \
+        git=1:2.25.1-1ubuntu3.11 \
+        wget=1.20.3-1ubuntu2 \
+        make=4.2.1-1.2 \
+        autotools-dev=20180224.1 \
+        autoconf=2.69-11.1 \
+        libtool=2.4.6-14 \
+        xz-utils=5.2.4-1ubuntu1.1 \
+        libffi-dev=3.3-4 \
+        libncurses-dev=6.2-0ubuntu2.1 \
+        libsqlite3-dev=3.31.1-4ubuntu0.5 \
+        libusb-1.0-0-dev=2:1.0.23-2build1 \
+        libudev-dev=245.4-4ubuntu3.22 \
+        gettext=0.19.8.1-10build1 \
+        pkg-config=0.29.1-0ubuntu4 \
+        libdbus-1-3=1.12.16-2ubuntu2.3 \
+        libpcsclite-dev=1.8.26-3 \
+        swig=4.0.1-5build1 \
+        libxkbcommon-x11-0=0.10.0-1 \
+        libxcb1=1.14-2 \
+        libxcb-icccm4=0.4.1-1.1 \
+        libxcb-image0=0.4.0-1build1 \
+        libxcb-keysyms1=0.4.0-1build1 \
+        libxcb-randr0=1.14-2 \
+        libxcb-render-util0=0.3.9-1build1 \
+        libxcb-render0=1.14-2 \
+        libxcb-shape0=1.14-2 \
+        libxcb-shm0=1.14-2 \
+        libxcb-sync1=1.14-2 \
+        libxcb-util1=0.4.0-0ubuntu3 \
+        libxcb-xfixes0=1.14-2 \
+        libxcb-xinerama0=1.14-2 \
+        libxcb-xkb1=1.14-2 \
+        libx11-xcb1=2:1.6.9-2ubuntu1.6 \
+        autopoint=0.19.8.1-10build1 \
+        zlib1g-dev=1:1.2.11.dfsg-2ubuntu1.5 \
+        libfreetype6=2.10.1-2ubuntu0.3 \
+        libfontconfig1=2.13.1-2ubuntu3 \
+        libssl-dev=1.1.1f-1ubuntu2.20 \
+        rustc=1.70.0+dfsg0ubuntu1~bpo2-0ubuntu0.20.04.1 \
+        cargo=1.70.0+dfsg0ubuntu1~bpo2-0ubuntu0.20.04.1 \
+        g++=4:9.3.0-1ubuntu2 \
+        && \
+    rm -rf /var/lib/apt/lists/* && \
+    apt-get autoremove -y && \
+    apt-get clean

contrib/build-linux/appimage/Dockerfile_ub2004

@@ -46,7 +46,7 @@ if [ -z ${SUDO+x} ] ; then
     fi
 fi
 
-DOCKER_SUFFIX=ub1804
+DOCKER_SUFFIX=ub2004
 
 info "Creating docker image ..."
 $SUDO docker build --progress plain -t electroncash-appimage-builder-img-$DOCKER_SUFFIX \