paraview_client: add -platform xcb for non-Apple non-Windows builds
Wayland is becoming more prevalent and VTK doesn't support it yet, so tell Qt that the clients want the xcb platform, not Wayland.
Fixes: #19481 (closed)
Untested for actual effect; I'm not using Wayland locally. I can see that the QApplication ctor gets the right data locally with this change:
Breakpoint 1, 0x00007ffff761d490 in QApplication::QApplication(int&, char**, int) () from /lib64/libQt5Widgets.so.5
(gdb) p *(((char**)$rdx)+0)
$1 = 0x7fffffffb5e3 "/home/boeckb/misc/builds/paraview/build/bin/paraview"
(gdb) p *(((char**)$rdx)+1)
$2 = 0x7fffffffb0e0 "-platform"
(gdb) p *(((char**)$rdx)+2)
$3 = 0x7fffffffb100 "xcb"
(gdb) p *(((char**)$rdx)+3)
$4 = 0x0