Android: First ever running arm64 version for the mobile app ...

[Jan Mulder]

... with working Bluetooth download :-)

After a long period of absence from Subsurface, Dirk was successful in 
motivating me again to work on something. So, I took on the challenge to 
get the Android mobile app running in arm64 mode working for BT/BLE 
downloads from DC.

People here might remember that the arm build was working, but the arm64 
build was persistently crashing hard on any BT/BLE interaction. Which 
would become a huge issue, as Google is going to kick out apps from its 
Play store, that are not supported on both arm and arm64 architectures 
any time soon.

Always having the idea that the BT download issue could be Qt related, 
my first plan was to build against a newer Qt, as reporting bugs to Qt 
is likely not going to be very successful when running older Qt version.

So, step 1. Upgraded to Qt 5.12.4 (Qt 13.0 still to be tested). This 
opened a can of worms, as we were still running a 1.0 OpenSSL version. 
The step to 1.1 OpenSSL appeared to be the major hurdle in this process 
(and the pull request the will follow tomorrow will show why). In 
addition some gradle plugin updates, and all builds again (locally).

And @Berthold. 
https://github.com/Subsurface-divelog/subsurface/issues/2167 is not 
reproducible on the arm64 build (but persistent on the arm build). So, I 
believe its likely memory corruption somewhere, but had no time to 
investigate this any further.

@Dirk. I did not do any Docker things (yet), but very likely, a new 
Docker image is needed in this process.

--jan