`checkRequiredEntryPoints` no longer accepts `android_main` as an
Android entry — `#jni_main #jni_class("...")` is now the sole accepted
path. The diagnostic walks the user through declaring an Activity +
Bundle foreign decl. `isExportedEntryName` drops `android_main` and
`ANativeActivity_onCreate` (both were for the legacy NativeActivity
glue path R.2 stopped linking by default).
Migrates the two cross-compile examples that previously carried an
`android_main` trampoline to a minimal `#jni_main #jni_class(...) { }`
stub:
- `examples/ffi-jni-call-02-void.sx` — tests `#jni_call(void)` lowering
- `examples/ffi-objc-call-10-os-gate.sx` — tests `inline if OS` gating
Both stubs are empty (no `onCreate` body) so they exercise the
entry-point check + R.3's JNI-symbol synthesis pass produces no
symbols. 131 host / 4 cross / zig build test all green.
`examples/99-android-egl-clear.sx` still uses `android_main` and the
AndroidPlatform/native_app_glue stack — its Android-target build now
fails the entry-point check. R.5 removes it along with the rest of
the legacy NativeActivity surface.
109/109 host tests pass; tests/cross_compile.sh's first real tuple
(`android | examples/ffi-objc-call-10-os-gate.sx`) compiles
through `sx build --target android` without finding any
`@objc_msgSend` / `@sel_registerName` symbols in the output —
the `inline if OS == .ios { #objc_call(...) }` arm is stripped
at sx compile time before emit_llvm runs, so the Android
toolchain (Bionic + libGLESv3 / NDK linker) doesn't see the
Obj-C runtime references that would otherwise be undefined.
Host (macOS): the example prints "host stripped both" — the iOS
arm is stripped (we're not iOS) AND the Android arm is stripped
(we're not Android), confirming `inline if OS == { case }`
symmetric strip-and-render works around `#objc_call` sites.
The example carries a 3-line `android_main` trampoline so the
NDK linker's `-u ANativeActivity_onCreate` / entry-point
discovery is satisfied — pattern shared with chess + the other
android examples.
