ci: add temporary cygwin build

Add a temporary Cygwin build to the PR CI while we work on Cygwin
compatibility.

We will move this to the nightlies when it is green.

.github/workflows/main.yml

@@ -121,6 +121,18 @@ jobs:
             BUILD_PATH: D:\Temp\mingw32\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Program Files (x86)\CMake\bin
             SKIP_SSH_TESTS: true
             SKIP_NEGOTIATE_TESTS: true
+        - name: "Windows (amd64, Cygwin)"
+          id: windows-amd64-cygwin
+          os: windows-2019
+          setup-script: cygwin
+          shell: D:\Temp\cygwin\bin\bash.exe --login --norc -eo pipefail -o igncr '{0}'
+          continue-on-error: true
+          env:
+            ARCH: amd64
+            CMAKE_OPTIONS: -DDEPRECATE_HARD=ON -DUSE_SSH=ON
+            BUILD_TEMP: D:\Temp
+            SKIP_NEGOTIATE_TESTS: true
+            BUILD_PATH: /bin:/usr/bin:/usr/local/bin:/sbin:/usr/sbin:/usr/local/sbin
 
         # All builds: reftable
         - name: "Linux (Noble, GCC, OpenSSL, libssh2, reftable)"

ci/setup-cygwin-build.sh

@@ -0,0 +1,35 @@
+#!/bin/sh
+
+set -ex
+
+echo "##############################################################################"
+echo "## Downloading cygwin"
+echo "##############################################################################"
+
+BUILD_TEMP=${BUILD_TEMP:=$TEMP}
+BUILD_TEMP=$(cygpath $BUILD_TEMP)
+
+case "$ARCH" in
+        amd64)
+                CYGWIN_URI="https://cygwin.com/setup-x86_64.exe";
+                ARCHIVE_URI="https://mirrors.kernel.org/sourceware/cygwin";;
+        x86)
+                CYGWIN_URI="https://cygwin.com/setup-x86.exe";
+                ARCHIVE_URI="https://mirrors.kernel.org/sourceware/cygwin-archive/20221123";;
+esac
+
+if [ -z "$CYGWIN_URI" ]; then
+        echo "No URL"
+        exit 1
+fi
+
+mkdir -p "$BUILD_TEMP"
+mkdir -p "$BUILD_TEMP/setup"
+mkdir -p "$BUILD_TEMP/packages"
+mkdir -p "$BUILD_TEMP/cygwin"
+
+curl -s -L "$CYGWIN_URI" -o "$BUILD_TEMP"/setup/cygwin-"$ARCH".exe
+
+"$BUILD_TEMP"/setup/cygwin-"$ARCH".exe -qgnO -l "$BUILD_TEMP/packages" -R "$BUILD_TEMP/cygwin" -s "$ARCHIVE_URI" -P gcc-core,make,ninja,cmake,autotools,zlib-devel,libssl-devel,libssh2-devel,libpcre2-devel,libiconv-devel,python3,git,openssh --allow-unsupported-windows
+
+echo BUILD_WORKSPACE="/cygdrive$(cygpath "${GITHUB_WORKSPACE}")" >> $GITHUB_ENV