Add an integration test with Docker

Dockerfile

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+FROM archlinux:latest
+
+# Install dependencies.
+ARG mirror_country=US
+RUN curl "https://www.archlinux.org/mirrorlist/?country=$mirror_country&protocol=https&ip_version=4&use_mirror_status=on" \
+    | sed --expression "s/^#//" \
+    > /etc/pacman.d/mirrorlist \
+ && pacman -Syyu --noconfirm --needed \
+ && pacman -S --noconfirm --needed \
+      ansible \
+      base-devel \
+      sudo
+
+# Create aur_builder user.
+RUN useradd --create-home --group=wheel aur_builder \
+ && echo 'aur_builder ALL=(ALL) NOPASSWD: /usr/bin/pacman' \
+    > /etc/sudoers.d/11-install-aur_builder \
+ && visudo -c -f /etc/sudoers.d/11-install-aur_builder \
+ && chmod 0644 /etc/sudoers.d/11-install-aur_builder
+
+# Run the playbook.
+WORKDIR /opt
+COPY library/ ./library/
+COPY integration-test.yml ./
+RUN ansible-playbook --module-path library integration-test.yml