Add checks to qmake for wayland/x11

[loonycyborg]

This makes surface page appear for me with my usual way of building with qmake/make without having to pass any extra defines to it.

[SaschaWillems]

Before merging this: Will this still work with CI?

[loonycyborg]

I did add pkg-config check that was needed to address systems that don't have wayland client development files installed. Seems CI for PR did pass too.

[SaschaWillems]

Right now I use defines to build wayland/x11 versions, see e.g. https://github.com/SaschaWillems/VulkanCapsViewer/blob/master/.github/workflows/build.yml#L38

And I'm unsure if this PR won't break my CI builds by creating applications that seemingly compile and build but fail at runtime.

[loonycyborg]

Only testing can tell for sure but CI doesn't seem to make artifacts available. Theoretically both pre-pr and post-pr builds should match with the exception of wayland build that would have x11 codepath also included. Due to PR #233 wayland will still be preferred in that case.