Fix crash with qt6 and multimedia plugin

[smarttowel]

Qt6 doesn't contain plugins/mediaservice dir

[TheAssassin]

Could you provide a link to a build log, please? Or at least a log excerpt.

[vadi2]

Qt6 does ship multimedia, and it would be important to still support it: https://doc.qt.io/qt-6/qtmultimedia-index.html

[TheAssassin]

This is what I thought as well. I'm curious to see how the plugin "crashes". I am pretty sure we just have to improve the deployer.

[smarttowel]

It's exception from boost::filesystem on missed mediaservice dir:

what():  boost::filesystem::directory_iterator::construct: No such file or directory: "/home/pavel/Qt/6.3.1/gcc_64/plugins/mediaservice"
ERROR: Failed to run plugin: qt (exit code: 6)```

[TheAssassin]

Please add either the complete log or at least the (possibly censored) Qt plugin log.

[smarttowel]

log.txt

[smarttowel]

About multimedia architecture in Qt6

[smarttowel]

@TheAssassin What you think about it?

[LarsHaalck]

I had the same problem and this PR fixes all issues for me.

[TheAssassin]

Thanks!