Support for armv8 arch only devices

[nfynt]

Recent pixel devices do not report armv7 arch support and only arm64-v8a. This causes benchmark test to exit early with message stating "Not an ARMv7 and not an X86 SSSE3 CPU !\n".

This update includes check for ANDROID_CPU_FAMILY_ARM64 along with subsequent cmake and gradle updates for running the test app.

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[DanAlbert]

I think you probably need to update https://github.com/android/ndk-samples/blob/ece52f26503987bbfd2ded8c73ffde05c457d035/hello-neon/app/src/main/cpp/helloneon-intrinsics.c#L18?

[DanAlbert]

Actually it was the CMakeLists.txt that needed updating. Pushed the fix to your branch.