fix: automate arch packaging

using docker just like debian. This makes the scripts easier to
reproduce.

arch-builder.dockerfile

@@ -0,0 +1,15 @@
+FROM archlinux
+RUN pacman -Sy --noconfirm base-devel
+ARG DOCKER_USER=arch
+
+# Set user and group
+ARG user=appuser
+ARG group=appuser
+ARG uid=1000
+ARG gid=1000
+RUN groupadd -g ${gid} ${group}
+RUN useradd -u ${uid} -g ${group} -s /bin/sh -m ${user} # <--- the '-m' create a user home directory
+ENV USER=${user}
+
+# Switch to user
+USER ${uid}:${gid}