The Ant build hasn't been runnable since the SDK dropped tools/ant/, so build.xml,
custom_rules.xml, ab-ant.sh, ant-build.bat, project.properties and
proguard-project.txt all go. Plus some orphans: buildassets.sh (nothing called it),
build.sh (still referred to "phoenix"), symx86.cmd (x86 isn't in APP_ABI) and
README.TXT (Eclipse import instructions).
ab.sh and ab.cmd no longer copy assets into android/assets - only the Ant/Eclipse
packaging ever read that directory. Gradle packages the repo-root assets/ directly
and ndk-build doesn't look at assets at all, so the stray copy only made it unclear
where the APK's assets come from. Noted how that actually works in docs/building.md.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The legacy android/jni build (ab.sh / ab.cmd / CI) used an ancient NDK
(r21e) and hardcoded job counts. Update it to the NDK version used by the
gradle build (29.0.14206865) and derive the job count from the available
cores (nproc / NUMBER_OF_PROCESSORS) instead of hardcoding.
