meson: Define ANDROID and ANDROID_API_LEVEL when compiling for Android

Set ANDROID_API_LEVEL based on the value we already have and define
ANDROID to make sure we build code paths that are guarded by that.

Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6112>
1 file changed