[qt-base] Use opengl dynamic configuration

[andrm]

This setting lets Qt use the ANGLE library and makes rendering on DirectX / Direct3D possible. OpenGL backends are switchable at runtime.

[msftclas]

All CLA requirements met.

[vicroms]

Hi @andrm

Thanks for your contribution!

qt5-base fails to build on Linux with the following message:

CMake Error at ports/qt5-base/install_qt.cmake:33 (file):
  file COPY cannot copy file "/usr/bin/flex" to "/usr/bin/bin/flex".
Call Stack (most recent call first):
  ports/qt5-base/portfile.cmake:147 (install_qt)
  scripts/ports.cmake:71 (include)


Error: Building package qt5-base:x64-linux failed with: BUILD_FAILED

You should wrap the relevant code inside an if block like this

if (CMAKE_HOST_WIN32)
   # your code
endif()

[Neumann-A]

What is Qt default here? I would prefer to use the default and have whatever is not the default be a feature flag.

[andrm]

Thank you very much for the quick responses and critques. I will re-work the PR.
Dynamic is the default in the pre-built packages from qt.io since 5.5. The page at https://doc.qt.io/qt-5/windows-requirements.html says this:
"Note: As of Qt 5.5 this is the configuration used by the official, pre-built binary packages of Qt. It is strongly recommended to use it also in custom builds, especially for Qt binaries that are deployed alongside applications."

[andrm]

You should wrap the relevant code inside an if block like this

if (CMAKE_HOST_WIN32)
   # your code
endif()

Ok, done.

[andrm]

I think I've addressed all issues, can you please re-check the PR?

[vicroms]

Thanks for the PR!
Everything looks OK now.