Drop Android x86_64 build

[brody4hire]

I would like to drop the Android NDK build for x86_64 CPU. NDK x86 (32-bit) build will also work on x86_64 CPU. One less CPU to test NDK builds on. (My understanding is that Android x86 and x86_64 CPU builds are generally used for the emulator.)

Objections and any other feedback would be very welcome, I would be happy to reconsider if there are enough objections.

[Dizzzlectic]

You are absolutely right. x86 and x86_64 are mainly used for emulators having different optimizations depending on CPU architecture.

[brody4hire]

Keeping x86_64 build for now