meson: setup first part for building on Android

This is the first MR for android, setting up the sources and fixing the blockers (speex and svg mainly) to have the core building with

╰─$ meson setup --wipe --cross-file android.crossfile --cross-file contrib/aarch64-linux-android/share/meson/cross/contrib.ini build-meson-android -Dchromecast=disabled -Dfreetype=disabled -Dskins2=auto -Dnvdec=auto -Dpng=disabled -Dlua=disabled