describe how to use msys2 packages on Windows

vcpkg-overlays/full-distro/windows-11/README.md

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+# How to Avoid Building All Dependencies with vcpkg
+
+vcpkg supports a trick that lets toy get a dependency from an external source  (like a package manager) instead of
+building it. The only explanation of the trick that I've seen is a [blog post from microsoft], but I've put it to
+use it on Linux (with apt/dnf dependencies), macOS (homebrew), and Windows (msys2).
+
+You can probably get away with using a different package manager, as long as the packages that it installs are
+registered with the pkg-config that your build uses. I've been getting pkg-config from msys2 on Windows, so I
+stayed with msys2 for the dependency packages as well. I imagine chocolatey would work too if that's your thing.
+
+Anyway, here's what worked for me:
+
+1. Install [msys2](https://www.msys2.org)
+
+2. Install pkg-config and ziti-tunnel-sdk-c dependencies from an `msys2` prompt:
+
+       pacman -S mingw-w64-x86_64-pkg-config mingw-w64-x86_64-protobuf-c mingw-w64-x86_64-json-c mingw-w64-x86_64-libuv \
+           mingw-w64-x86_64-libsodium mingw-w64-x86_64-openssl 
+
+3. Add `c:\msys64\mingw64\bin` to your PATH.
+
+4. Add the following to your cmake preset:
+
+       "cacheVariables": {
+          "VCPKG_OVERLAY_PORTS": "${sourceDir}/vcpkg-overlays/full-distro/windows-11"
+       },
+       "environment": {
+          "OPENSSL_ROOT_DIR": "c:/msys64/mingw64"
+       },
+
+   The openssl variable was needed because [cmake's FindOpenSSL module](https://cmake.org/cmake/help/latest/module/FindOpenSSL.html)
+   does not consult `pkg-config` on Windows.
+
+5. Remove your build directory, and re-run cmake.

vcpkg-overlays/full-distro/windows-11/json-c/portfile.cmake

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+set(VCPKG_POLICY_EMPTY_PACKAGE enabled)

vcpkg-overlays/full-distro/windows-11/json-c/vcpkg.json

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+{
+  "name": "json-c",
+  "version": "0"
+}

vcpkg-overlays/full-distro/windows-11/libsodium/portfile.cmake

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+set(VCPKG_POLICY_EMPTY_PACKAGE enabled)

vcpkg-overlays/full-distro/windows-11/libsodium/vcpkg.json

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+{
+  "name": "libsodium",
+  "version": "0"
+}

vcpkg-overlays/full-distro/windows-11/libuv/portfile.cmake

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+set(VCPKG_POLICY_EMPTY_PACKAGE enabled)

vcpkg-overlays/full-distro/windows-11/libuv/vcpkg.json

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+{
+  "name": "libuv",
+  "version": "0"
+}

vcpkg-overlays/full-distro/windows-11/openssl/portfile.cmake

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+set(VCPKG_POLICY_EMPTY_PACKAGE enabled)

vcpkg-overlays/full-distro/windows-11/openssl/vcpkg.json

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+{
+  "name": "openssl",
+  "version": "0"
+}

vcpkg-overlays/full-distro/windows-11/protobuf-c/portfile.cmake

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+set(VCPKG_POLICY_EMPTY_PACKAGE enabled)

vcpkg-overlays/full-distro/windows-11/protobuf-c/vcpkg.json

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+{
+  "name": "protobuf-c",
+  "version": "0"
+}