NDK r24 support

[mchinen]

r24 isn't supported in master due to the toolchain path changes after r21. On the 'pre-alpha' branch, this warning and error appears when using r24 NDK (and I suppose r22 and r23). Is there a workaround for supporting r24 in bazel? If not, is it reasonable to use SDK 30 with r21?

WARNING: The major revision of the Android NDK referenced by android_ndk_repository rule 'androidndk' is 24. The major revisions supported by Bazel are [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21]. Bazel will attempt to treat the NDK as if it was r21. This may cause compilation and linkage problems. Please download a supported NDK version. ERROR: /usr/local/google/home/mchinen/scm/lyra/android_example/BUILD:26:16: While resolving toolchains for target //android_example:lyra_android_lib: no matching toolchains found for types @rules_android//toolchains/android:toolchain_type, @rules_android//toolchains/android_sdk:toolchain_type ERROR: /usr/local/google/home/mchinen/scm/lyra/android_example/BUILD:46:15: While resolving toolchains for target //android_example:lyra_android_example_RESOURCES_DO_NOT_USE: no matching toolchains found for types @rules_android//toolchains/android:toolchain_type

[keith]

Most of the discussion about this is here: bazelbuild/bazel#12889

we're using ndk 21 in the meantime and it works fine as long as you don't need any newer features / improvements from newer NDKs

[cpsauer]

@keith with his usual set of blazingly fast, great cross-refs :)
@mchinen Would you be down to close this one and centralize around bazelbuild/bazel#12889, esp since the code for this is still in Bazel core?

[mchinen]

@keith thank you for the info!
@cpsauer sure, if you prefer that, feel free to close. I will make a weak case for leaving it open while following the bazel core issue: it will help with visibility since bazel core issues are so numerous that it is not easy to view/search and others might come to this repo for android build rule failures.

[cpsauer]

Up to you guys! (I don't have magic closing power.)
[If someone reading this knows the Bazel philosophy around when issues should be centralized vs federated, I'd be curious to hear.]

[ahumesky]

NDK support is being moved to github.com/bazelbuild/rules_android_ndk, and there's a development preview that should work for NDK 25. As mentioned above, the discussion is on bazelbuild/bazel#12889