Use [cargo-ndk](https://github.com/bbqsrc/cargo-ndk) to configure cargo for building with the Android NDK. The output of `cargo ndk` is written to a subfolder for the target triplet, which cannot be changed by parameter. Therefore, the `CARGO_BUILD_DIR` is changed to this subfolder for the Android build, so the build process can find the output.
Use `$HOME` instead of `~` because cargo-ndk cannot correctly access the folder otherwise (will fail with error message indicating it could not determine the NDK version).
Add `DDNET_TEST_NO_LINK=ON` CMake argument, to fix Rust linking errors with tests.
Add additional CMake arguments to specify system name, API version and NDK location. Upgrade to Android API 34.
Use `nproc` instead of `32` threads for building.
