src-tauri/.cargo/config.toml hardcoded absolute NDK paths under
/home/dtourolle, which only exist on the dev laptop. In CI this made
ring's build script fail to find aarch64-linux-android34-clang. Tauri
derives the linker/CC paths from NDK_HOME automatically during
'android build', so the file is unnecessary there. Untrack it and
gitignore it; local dev copies are preserved on disk.
