[qtkeychain] Fix the CMake export target on windows

[daschuer]

It turns out that the fix from #24013 that allows to use CMake < 3.18 does not work on windows. This adds a patch that reintroduces the alias solution but under a cmake version guard.
I have propose this also upstream frankosterfeld/qtkeychain#212, but did not yet get a responds since May 8th.

• What does your PR fix?

It fixes the exported CMake target on windows

• Which triplets are supported/not supported? Have you updated the CI baseline?

No change

• Does your PR follow the maintainer guide?

Yes

• If you have added/updated a port: Have you run ./vcpkg x-add-version --all and committed the result?

Yes

[JonLiu1993]

I tested the usage successfull :

1> CMake generation started for configuration: 'x64-Debug'.
1> Command line: "C:\WINDOWS\system32\cmd.exe" /c "%SYSTEMROOT%\System32\chcp.com 65001 >NUL && "C:\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\2019\ENTERPRISE\COMMON7\IDE\COMMONEXTENSIONS\MICROSOFT\CMAKE\CMake\bin\cmake.exe"  -G "Visual Studio 16 2019" -A x64  -DCMAKE_CONFIGURATION_TYPES:STRING="Debug" -DCMAKE_INSTALL_PREFIX:PATH="C:\Users\test\source\repos\CMakeProject42\out\install\x64-Debug" -DCMAKE_TOOLCHAIN_FILE=F:/Feature-test/qtkeychain/vcpkg/scripts/buildsystems/vcpkg.cmake "C:\Users\test\source\repos\CMakeProject42" 2>&1"
1> Working directory: C:\Users\test\source\repos\CMakeProject42\out\build\x64-Debug
1> [CMake] -- Selecting Windows SDK version 10.0.19041.0 to target Windows 10.0.19042.
1> [CMake] -- The C compiler identification is MSVC 19.29.30145.0
1> [CMake] -- The CXX compiler identification is MSVC 19.29.30145.0
1> [CMake] -- Detecting C compiler ABI info
1> [CMake] -- Detecting C compiler ABI info - done
1> [CMake] -- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Enterprise/VC/Tools/MSVC/14.29.30133/bin/Hostx64/x64/cl.exe - skipped
1> [CMake] -- Detecting C compile features
1> [CMake] -- Detecting C compile features - done
1> [CMake] -- Detecting CXX compiler ABI info
1> [CMake] -- Detecting CXX compiler ABI info - done
1> [CMake] -- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Enterprise/VC/Tools/MSVC/14.29.30133/bin/Hostx64/x64/cl.exe - skipped
1> [CMake] -- Detecting CXX compile features
1> [CMake] -- Detecting CXX compile features - done
1> [CMake] -- Configuring done
1> [CMake] -- Generating done
1> [CMake] -- Build files have been written to: C:/Users/test/source/repos/CMakeProject42/out/build/x64-Debug
1> Extracted CMake variables.
1> Extracted source files and headers.
1> Extracted code model.
1> Extracted toolchain configurations.
1> Extracted includes paths.
1> CMake generation finished

[daschuer]

The upstream PR has just been merged.
I think I will pick the merge commit on master to avoid the patch. The resulting source is identical.

[daschuer]

This PR is still needed to pull the upstream changes in. But we can point to the particular comit instead of using a patch with the same content. I will prepare this tonight.

[daschuer]

Done. @JonLiu1993 can you have another look? I have also updated the qt6 version.

[JonLiu1993]

LGTM, thanks for your pr!

[ras0219-msft]

This LGTM, thanks for the fix!