Add new port: graphics/qt5-wayland

[tcberner]

Summary

Marketing blurb [1]:

QtWayland is a Qt 5 module that wraps the functionality of Wayland. 
QtWayland is separated into a client and server side. The client side 
is the wayland platform plugin, and provides a way to run Qt applications 
as Wayland clients. The server side is the QtCompositor API, and allows
users to write their own Wayland compositors.

This is mostly needed at the moment to make upstream KDE-CI happy, therefore
we don't wire it into the metaport devel/qt5.

It requires a little change to devel/qt5-qmake, as we needed to modify the
installed bsd.conf to know about wayland/egl.

(Created together with [ade]).

[1] https://wiki.qt.io/QtWayland

Test Plan

Build devel/qt5, to see that we did not again break it :)

[tcberner]

graphics/qt5-wayland/files/patch-qtwayland.pro

5 ↗

(On Diff #31229)

Oh, I forgot about this ^^ -- I did/do not remember/know how to do an 'or' in qmake in that context =)

[tcberner]

Add nicer check in files/patch-qtwayland.pro as suggested by [ade] in irc.

[tcberner]

@rakuco le ping, le pong

[adridg]

devel/qt5/Makefile

11 ↗

(On Diff #31232)

Should probably adjust the comment, too.

graphics/qt5-wayland/Makefile

9 ↗

(On Diff #31232)

"Qt5 wrapper for Wayland" instead of this klunker.

[rakuco]

lgtm modulo ade's comments. Overall, I think it's good to go!