When cargo call-stack is called through cargo, the argv it sees is the unmodified `['cargo', 'call-stack', '--target', 'some-triple-triple', 'mystartsym']. Thus, the parser reports the start argument "mystartsym" as unexpected argument.

I'm not sure how this is best fixed; for a workaround, I'm calling it as ~/.cargo/bin/cargo-call-stack instad of cargo call-stack; this appears to necessitate setting a rustup override for nightly (as there is no place to put the +nightly).