Include option to use LLVM for users with Qt < 5.14
When NDK r20+ is used along with Qt5.12, APK generation fails because of the layout change in newer NDK. This patch introduces a new variable USE_LLVM, when this is set for older Qt versions, androiddeployqt uses LLVM's tools.
(I had to write this because Krita is updating to the newer NDK and we still use Qt5.12 :) )
Edited by Sharaf Zaman