CI counterpart to
https://bugreports.qt.io/browse/QTBUG-55981 introduces Vulkan support on some platforms.
The dependency is header only, meaning there is no direct linking to any libaries. The Vulkan headers must however be present in order to get the feature enabled by configure.
On Windows the process of this is to install the LunarG Vulkan SDK from https://www.lunarg.com/vulkan-sdk/ which then sets a VULKAN_SDK environment variable. Qt builds will automatically pick this up, thus to get Vulkan-capable builds (that still do not require the presence of a Vulkan library at run time) no further steps are needed apart from making sure the build machine has the SDK installed.
In order to test at least compilation of the Vulkan support, at least some of the Windows MSVC configurations should be updated so that the SDK is part of the VM and thus Qt's Vulkan support gets enabled at configure time.