arm64-v8a ABI is not supported in NdkCxxPlatform

[ide]

This is for 64-bit ARMv8-a support: https://developer.android.com/ndk/guides/abis.html#arm64-v8a

[sdwilsh]

This should be as simple as adding a new entry in `NdkCxxPlatforms`, if you happen to feel mildly ambitious.

[LegNeato]

More specifically here:

buck/src/com/facebook/buck/android/NdkCxxPlatforms.java

Line 169 in ad8f8c2

NdkCxxPlatform armeabiv7 =

[sdwilsh]

4abf4af is an example of how to add another platform as well.

[ajtulloch]

@LegNeato were you planning on PR'ing LegNeato@9e14600?

[LegNeato]

@ajtulloch Not currently. Mainly because it has probably bitrotted and I don't have a test project to muck around with to make sure everything works correctly.

[dreiss]

This looks fine to me, though the default flags should be updated to match https://android.googlesource.com/platform/ndk.git/+/nougat-release/build/core/toolchains/aarch64-linux-android-4.9/setup.mk .

[dreiss]

@LegNeato , can you PR it just so we can use our normal import/CLA machinery? We can probably get someone else to handle the rebase, cleanup, and test.

[LegNeato]

It actually rebased cleanly. I'll PR, do you want me to update the flags? I can't really test anything 😄

[ajtulloch]

@LegNeato sure, that would be great. We'll test internally.