Add GitHub workflow for building XRT on windows using public runners

.github/containers/windows/Dockerfile

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+# Windows container for building XRT with cl.exe (MSVC) and vcpkg.
+# Build: docker build -t xrt-build:windows -m 2GB .
+# Run (interactive): docker run -it -v C:\path\to\XRT:C:\XRT xrt-build:windows
+# Then inside container: cd C:\XRT && .\build\build22.bat -opt
+# Or use this image as the runner image for a self-hosted GitHub Actions Windows runner.
+# escape=`
+
+FROM mcr.microsoft.com/windows/servercore:ltsc2022
+
+SHELL ["cmd", "/S", "/C"]
+
+RUN `
+    curl -SL --output vs_buildtools.exe https://aka.ms/vs/17/release/vs_buildtools.exe `
+    && (start /w vs_buildtools.exe --quiet --wait --norestart --nocache `
+        --installPath "%ProgramFiles(x86)%\Microsoft Visual Studio\2022\BuildTools" `
+        --add Microsoft.VisualStudio.Workload.VCTools `
+        --remove Microsoft.VisualStudio.Component.Windows10SDK.10240 `
+        --remove Microsoft.VisualStudio.Component.Windows10SDK.10586 `
+        --remove Microsoft.VisualStudio.Component.Windows10SDK.14393 `
+        --remove Microsoft.VisualStudio.Component.Windows81SDK `
+        || IF "%ERRORLEVEL%"=="3010" EXIT 0) `
+    && del /q vs_buildtools.exe
+
+# Git and vcpkg: install when running the container, or add further RUN steps here.
+# The GitHub Actions workflow uses the host's Git and clones vcpkg in the job.
+
+# Developer command prompt + PowerShell (cl.exe in PATH)
+ENTRYPOINT ["C:\\Program Files (x86)\\Microsoft Visual Studio\\2022\\BuildTools\\Common7\\Tools\\VsDevCmd.bat", "-arch=amd64", "&&", "powershell.exe", "-NoLogo", "-ExecutionPolicy", "Bypass"]

.github/containers/windows/README.md

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+# Windows container for building XRT
+
+This directory contains a Dockerfile for building XRT on Windows inside a Docker container using **cl.exe** (MSVC) and **vcpkg** for dependencies.
+
+## Prerequisites
+
+- Windows host with Docker configured for Windows containers
+- Sufficient memory and disk (see [Microsoft's guide](https://learn.microsoft.com/en-us/visualstudio/install/build-tools-container))
+
+## Building the image
+
+From this directory (or repo root):
+
+```powershell
+docker build -t xrt-build:windows -m 2GB .github/containers/windows
+```
+
+Use `-m 2GB` or more; the default 1 GB is often insufficient for the Build Tools install.
+
+## Running a build inside the container
+
+1. Clone XRT and submodules on the host.
+2. Run the container with the repo mounted and use the vcpkg workflow (same as the GitHub Action):
+
+```powershell
+docker run -it -v C:\path\to\XRT:C:\XRT xrt-build:windows
+```
+
+Inside the container, the environment has `cl.exe` in PATH. Install or bring Git, CMake, and vcpkg (e.g. clone vcpkg and bootstrap it), then run the same configure/build steps as in `.github/workflows/build-windows.yml`: use the repo’s `src/vcpkg.json`, pass the vcpkg toolchain file to CMake, and set `KHRONOS` to the vcpkg installed directory (e.g. `vcpkg\installed\x64-windows`).
+
+## Using with GitHub Actions
+
+GitHub-hosted Windows runners do **not** support running the job inside a container. To run the Windows build in this container in CI:
+
+- Use a **self-hosted** Windows runner that has Docker (Windows containers) installed.
+- Build this image on that runner (or pull it from your registry).
+- In your workflow, run the build by executing the same CMake/vcpkg steps inside this container (e.g. with `docker run` and the appropriate volume and command).
+
+The main Windows workflow (`.github/workflows/build-windows.yml`) runs on `windows-latest` without a container so it works on GitHub-hosted runners.

.github/workflows/build-windows.yml

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+# Build XRT on Windows using cl.exe (MSVC) with vcpkg for 3rd party dependencies.
+# Note: GitHub-hosted Windows runners do not support running jobs inside a container.
+# For containerized builds, use a self-hosted runner with the Dockerfile in .github/containers/windows.
+name: Build XRT (Windows)
+
+on:
+  push:
+    branches: [master, main]
+  pull_request:
+    branches: [master, main]
+  workflow_dispatch:
+
+env:
+  VCPKG_BINARY_SOURCES: 'clear;nuget,https://pkgs.dev.azure.com/vcpkg/public/_packaging/public/nuget/v3/index.json,readwrite'
+
+jobs:
+  build-windows:
+    runs-on: windows-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Export GitHub Actions cache environment variables
+        uses: actions/github-script@v7
+        with:
+          script: |
+            core.exportVariable('ACTIONS_CACHE_URL', process.env.ACTIONS_CACHE_URL || '');
+            core.exportVariable('ACTIONS_RUNTIME_TOKEN', process.env.ACTIONS_RUNTIME_TOKEN || '');
+
+      - name: Set up vcpkg
+        uses: actions/checkout@v4
+        with:
+          repository: microsoft/vcpkg
+          path: vcpkg
+          ref: master
+
+      - name: Bootstrap vcpkg
+        run: .\vcpkg\bootstrap-vcpkg.bat -disableMetrics
+        working-directory: ${{ github.workspace }}
+
+      - name: Cache vcpkg packages
+        uses: actions/cache@v4
+        with:
+          path: |
+            ${{ github.workspace }}/vcpkg/installed
+            ${{ github.workspace }}/vcpkg/buildtrees
+            ${{ github.workspace }}/vcpkg/downloads
+          key: vcpkg-win-${{ runner.os }}-${{ hashFiles('src/vcpkg.json') }}
+          restore-keys: |
+            vcpkg-win-${{ runner.os }}-
+
+      - name: Install vcpkg dependencies (manifest)
+        run: |
+          .\vcpkg\vcpkg.exe install --x-manifest-root="${{ github.workspace }}\src" --triplet=x64-windows
+        working-directory: ${{ github.workspace }}
+
+      - name: Configure CMake (Release)
+        run: |
+          $vcpkgRoot = "${{ github.workspace }}\vcpkg"
+          $triplet = "x64-windows"
+          $kronos = "$vcpkgRoot\installed\$triplet"
+          $src = "${{ github.workspace }}\src"
+          $build = "${{ github.workspace }}\build\WRelease"
+          New-Item -ItemType Directory -Force -Path $build
+          cmake -B $build -S $src `
+            -G "Visual Studio 17 2022" -A x64 `
+            -DCMAKE_TOOLCHAIN_FILE="$vcpkgRoot\scripts\buildsystems\vcpkg.cmake" `
+            -DVCPKG_HOST_TRIPLET=$triplet `
+            -DKHRONOS="$kronos" `
+            -DCMAKE_EXPORT_COMPILE_COMMANDS=ON `
+            -DMSVC_PARALLEL_JOBS=4
+        shell: pwsh
+
+      - name: Build (Release)
+        run: |
+          $build = "${{ github.workspace }}\build\WRelease"
+          cmake --build $build --config Release --verbose
+        shell: pwsh
+
+      - name: Install (staging)
+        run: |
+          $build = "${{ github.workspace }}\build\WRelease"
+          $prefix = "$build\xilinx\xrt"
+          cmake --install $build --config Release --prefix $prefix --verbose
+        shell: pwsh
+
+      - name: Upload build artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: xrt-windows-Release
+          path: ${{ github.workspace }}/build/WRelease/xilinx/xrt
+          retention-days: 7

src/vcpkg.json

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+{
+  "name": "xrt",
+  "version": "0.1.0",
+  "description": "XRT Windows build dependencies (vcpkg manifest)",
+  "dependencies": [
+    "boost-filesystem",
+    "boost-program-options",
+    "gtest",
+    "opencl"
+  ]
+}