feat: Install VanillaOS' first-setup (#55)

Containerfile

@@ -1,8 +1,31 @@
+# Multi-stage build
 ARG FEDORA_MAJOR_VERSION=37
 
+## Build vanilla-first-setup
+FROM ubuntu:22.04 AS build
+
+RUN apt-get update && apt-get install -y \
+    build-essential meson libadwaita-1-dev \
+    gettext desktop-file-utils git
+
+# Checkout the last tested/known working commit, in liu of an upstream release
+RUN git clone https://github.com/Vanilla-OS/first-setup.git && \
+    cd first-setup && git checkout bf21de5
+WORKDIR first-setup
+RUN meson build --prefix /usr && ninja -C build
+RUN DESTDIR=/opt ninja -C build install
+RUN tar cfz vanilla-first-setup.tar.gz /opt
+
+## Build ublue-os-base
 FROM quay.io/fedora-ostree-desktops/silverblue:${FEDORA_MAJOR_VERSION}
 # See https://pagure.io/releng/issue/11047 for final location
 
+## Install the VanillaOS first-setup utility
+COPY --from=build /first-setup/vanilla-first-setup.tar.gz /
+RUN tar xf vanilla-first-setup.tar.gz --strip-component=1 -C / && \
+    chmod +x /usr/bin/vanilla-first-setup && \
+    ostree container commit
+
 COPY etc /etc
 
 COPY ublue-firstboot /usr/bin