Nightly regression: Can't perform LTO when compiling incrementally

[PvdBerg1998]

I updated to the nightly 2019-01-27 msvc from 2019-01-25 msvc and my release profile using lto = true broke.

The error message given is Can't perform LTO when compiling incrementally.

[Mark-Simulacrum]

Cc @michaelwoerister - related to Cargo release changes, I suspect.

[nagisa]

This is a cargo bug, with a fix at rust-lang/cargo#6610. Closing.