Lmms: LMMS 1.2.1 fails to build with Qt 5.15.0RC

[demmm]

Bug Summary

Qt 5.15 introduces the need to include QPainterPath. Try to build with 5.15.0-rc, and the build fails at multiple places due this missing include.

Steps to reproduce

Build with Qt 5.15
To workaround this issue, following patch was used, fixes the build, app runs properly with it:
https://github.com/KaOSx/apps/blob/master/lmms/qt5.15.diff

Affected LMMS versions

1.2.1

[JohannesLorenz]

@demmm Many thanks for reporting and analyzing!

I'll turn this into a PR now.

[JohannesLorenz]

Will be fixed by #5498 .

@demmm Can you please test if my fix works? Just clone https://github.com/JohannesLorenz/lmms.git, checkout fix/#5486 and see if it compiles.

[tresf]

Will be fixed by #5498

Merged, closing.