TUN-9803: Add windows builds to gitlab-ci

.ci/image/Dockerfile

@@ -0,0 +1,25 @@
+ARG CLOUDFLARE_DOCKER_REGISTRY_HOST
+
+FROM ${CLOUDFLARE_DOCKER_REGISTRY_HOST:-registry.cfdata.org}/stash/cf/debian-images/bookworm/main:2025.7.0@sha256:6350da2f7e728dae2c1420f6dafc38e23cacc0b399d3d5b2f40fe48d9c8ff1ca
+
+RUN apt-get update && \
+    apt-get upgrade -y && \
+    apt-get install --no-install-recommends --allow-downgrades -y \
+        build-essential \
+        git \
+        go-boring=1.24.4-1 \
+        libffi-dev \
+        python3-dev \
+        python3-pip \
+        python3-setuptools \
+        python3-venv \
+        # libmsi and libgcab are libraries the wixl binary depends on.
+        libmsi-dev \
+        libgcab-dev && \
+    rm -rf /var/lib/apt/lists/* && \
+    # Install wixl
+    curl -o /usr/local/bin/wixl -L https://pkg.cloudflare.com/binaries/wixl && \
+    chmod a+x /usr/local/bin/wixl && \
+    mkdir -p opt
+
+WORKDIR /opt