Add Android cdylib target and AAudio PCM sink
Introduce a headless Android "cdylib" target that builds Rockbox as a
static codec set for inclusion in an Expo native module. Add:
- CONFIG_BINFMT=BINFMT_STATIC and CODECS_STATIC static-link mode
- androidcdylib config header, lc-static/lc-android loader, and codecs
make
- AAudio PCM sink and pcm sink wiring for Android
- headless system shim, no-op LCD/button drivers, and rb_zig_compat C
wrappers for Zig-provided rb_*