Bad performance on iOS 14

[hansemannn]

Hey @AndreaVitale! I can reproduce your performance bug now as well. What should we do?

[hansemannn]

Ref on SDWebImage: SDWebImage/SDWebImage#3083

[AndreaVitale]

I merged your PR because the build with SDWebImage 5.8.2 seems to works fine.
In order to move forward with next SDWebImage updates we need to investigate on this so I will not close the issue.