Try to build a plain cygwin image

.github/workflows/main.yml

@@ -39,12 +39,14 @@ jobs:
       - name: Build images
         run: |
           docker build --tag ghcr.io/msys2/msys2-docker-experimental:latest ./msys2
+          docker build --tag ghcr.io/msys2/cygwin-docker-experimental:latest ./cygwin
           docker build --tag ghcr.io/msys2/msys2-docker-devcontainer:latest ./devcontainer
 
       - name: Save images
         if: github.event_name == 'pull_request'
         run: |
           docker image save ghcr.io/msys2/msys2-docker-experimental:latest | zstd -T0 -c > experimental.tar.zst
+          docker image save ghcr.io/msys2/cygwin-docker-experimental:latest | zstd -T0 -c > cygwin.tar.zst
           docker image save ghcr.io/msys2/msys2-docker-devcontainer:latest | zstd -T0 -c > devcontainer.tar.zst
 
       - name: Upload artifacts
@@ -63,4 +65,5 @@ jobs:
         if: github.event_name != 'pull_request'
         run: |
           docker push ghcr.io/msys2/msys2-docker-experimental:latest
+          docker push ghcr.io/msys2/cygwin-docker-experimental:latest
           docker push ghcr.io/msys2/msys2-docker-devcontainer:latest

cygwin/Dockerfile

@@ -0,0 +1,46 @@
+FROM ghcr.io/msys2/msys2-docker-build-base AS build
+
+# Install dependencies and download Cygwin setup
+RUN apt update && apt install -y --no-install-recommends curl ca-certificates
+
+# Download Cygwin setup executable
+RUN mkdir -p /tmp/cygwin
+RUN curl --fail -L 'https://www.cygwin.com/setup-x86_64.exe' -o /tmp/cygwin/setup-x86_64.exe
+
+FROM debian:trixie
+
+# Install runtime deps
+RUN apt update \
+    && apt install -y --no-install-recommends xvfb wine64 xauth ca-certificates \
+    && apt remove -y wine64 libwine \
+    && rm -rf /var/lib/apt/lists/*
+COPY --from=build /wine /
+RUN ldconfig
+
+# Avoid "tzset" startup warning + wineboot crashing
+ENV TZ=UTC
+
+# Initialize Wine
+RUN WINEDEBUG=-all wineboot --init && wineserver --wait
+
+# Copy Cygwin setup into Wine's filesystem
+COPY --from=build /tmp/cygwin/setup-x86_64.exe /tmp/setup-x86_64.exe
+
+# Install Cygwin via Wine
+RUN WINEDEBUG=-all xvfb-run -a wine /tmp/setup-x86_64.exe \
+    --quiet-mode \
+    --no-shortcuts \
+    --no-startmenu \
+    --no-desktop \
+    --root 'C:\cygwin64' \
+    --site 'https://mirrors.kernel.org/sourceware/cygwin/' \
+    --local-package-dir 'C:\cygwin64\packages' \
+    && wineserver --wait \
+    && rm -Rf  /root/.wine/drive_c/cygwin64/packages \
+    && mv /tmp/setup-x86_64.exe /root/.wine/drive_c/cygwin64/bin/setup.exe
+
+COPY ./cygwin /usr/bin/cygwin
+RUN chmod +x /usr/bin/cygwin
+
+WORKDIR /root/.wine/drive_c/cygwin64/home/root
+CMD ["cygwin"]

cygwin/cygwin

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+WINEDEBUG="-all" WINEPATH="C:\\cygwin64\\bin"  xvfb-run -a wine bash.exe -o igncr -l "$@"

docker-compose.yml

@@ -0,0 +1,27 @@
+services:
+  build-base:
+    build:
+      context: ./build-base
+    image: ghcr.io/msys2/msys2-docker-build-base:latest
+    pull_policy: never
+
+  msys2:
+    build:
+      context: ./msys2
+      additional_contexts:
+        ghcr.io/msys2/msys2-docker-build-base: "service:build-base"
+    image: ghcr.io/msys2/msys2-docker-experimental:latest
+
+  cygwin:
+    build:
+      context: ./cygwin
+      additional_contexts:
+        ghcr.io/msys2/msys2-docker-build-base: "service:build-base"
+    image: ghcr.io/msys2/cygwin-docker-experimental:latest
+
+  devcontainer:
+    build:
+      context: ./devcontainer
+      additional_contexts:
+        ghcr.io/msys2/msys2-docker-build-base: "service:build-base"
+    image: ghcr.io/msys2/msys2-docker-devcontainer:latest