musl is needed to enable static linking.
You can use the following instructions to install musl on Debian:
apt install musl-tools
Then you need to install the corresponding musl rust target (see rustc --print target-list | grep musl
):
rustup target add x86_64-unknown-linux-musl
Then compile with the features that do not require dynamic linking:
cargo build --target=x86_64-unknown-linux-musl --no-default-features --features vendored-openssl,vendored-c-ares