Auto merge of rust-lang#102332 - chriswailes:ndk-update, r=chriswailes

Update CI to use Android NDK r25b

This commit updates the CI definitions to use the most recent Android LTS NDK release: r25b.  Changes since the last NDK used by Rust negate the need to generate "standalone toolchains" and newer NDKs can be used in-place.

See https://developer.android.com/ndk/guides/other_build_systems#overview

Author: bors