Qt: Fix build with libepoxy and old versions of Qt5
Qt: Fix build with libepoxy and old versions of Qt5

Anty-Lemon/mgba,sergiobenrocha2/mgba,Iniquitatis/mgba,iracigt/mgba,fr500/mgba,mgba-emu/mgba,jeremyherbert/mgba,MerryMage/mgba,MerryMage/mgba,mgba-emu/mgba,iracigt/mgba,mgba-emu/mgba,sergiobenrocha2/mgba,Touched/mgba,AdmiralCurtiss/mgba,libretro/mgba,mgba-emu/mgba,Anty-Lemon/mgba,libretro/mgba,jeremyherbert/mgba,jeremyherbert/mgba,iracigt/mgba,jeremyherbert/mgba,fr500/mgba,Iniquitatis/mgba,fr500/mgba,AdmiralCurtiss/mgba,sergiobenrocha2/mgba,AdmiralCurtiss/mgba,fr500/mgba,libretro/mgba,iracigt/mgba,Touched/mgba,libretro/mgba,Touched/mgba,Iniquitatis/mgba,Anty-Lemon/mgba,libretro/mgba,MerryMage/mgba,Iniquitatis/mgba,sergiobenrocha2/mgba,Anty-Lemon/mgba,sergiobenrocha2/mgba