merge two if(SAILFISHOS) calls

2 jobs for master in 16 minutes and 3 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #20110
linux kf5-qt5 qt5.12

00:08:00

34.0%
passed #20111
windows
windows kf5-qt5 qt5.13

00:08:02