Suggestion: install neon packages to separate directory

[Pyroman]

> But it might be a reasonable guess that those of us who use Neon, this 
> non-distro, do so because of it having the latest official version of 
> Plasma available to us as soon as it is released, and it is possibly 
> more likely that newness of other software may be of value to many of us. 

I don't use latest software on all machines, upgrading only when sure 
that it's stable enough after testing. Current 5.18 Neon btw has some 
bugs that keeps me from upgrading (already reported).


> Maybe a list of the true number of programs affected would help?

I didn't try to install all Qt apps but here are two more:

Calibre: https://pastebin.com/VPSTRpTt
Musescore: https://pastebin.com/xhAdG7j4

In the past qtcreator was affected too: 
https://forum.kde.org/viewtopic.php?t=136886


> Why add the extra complication of such a setup
Is it really such an extra complication? I thought it's just specifying 
"/opt/neon" path as prefix at build time.