Ah, gotcha.
Yeah, the Standalone NDK is a bit of a pain since the .cargo/config requires absolute paths to the linker/ar. It makes it hard to commit a common config file for multiple people working in one repo.
I use a build script that takes environment variables https://github.com/myfreeweb/freepass/blob/706e8d9f25f08ac34... (and calls Cargo once per architecture. Android has many :D)
I use the executable name in the config and tell people to add $STANDALONE_NDK/bin to $PATH.
[target.arm-linux-androideabi]
ar = "arm-linux-androideabi-ar"
linker = "arm-linux-androideabi-gcc"
https://github.com/rust-lang/cargo/pull/3885/files#diff-27a1... would imply to me that oyu still need an NDK.