Add cdylib automically via --crate-type

[jbis9051]

Android requires the Cargo.toml to include

[lib]
crate-type = ["staticlib", "cdylib"]

This is problematic for users who also want to build for iOS. See rust-lang/cargo#4881.

Could this crate leverage rust-lang/cargo#10083 to add cdylib to all the rustc calls instead of requiring it to be specified in Cargo.toml?

[bbqsrc]

cargo-ndk is just a thin wrapper around cargo.

Try cargo ndk rustc --crate-type=cdylib.