Cargo crashes when compiled with LibreSSL. To fix this, it needs newer versions of some crates it depends on. See the following GitHub pull request:
https://github.com/rust-lang/cargo/pull/3521
Two FreeBSD users tested the patch in the pull request successfully. I tested the port with the OpenSSL from Ports.
The registry is also recreated because of those new crates.
PORTREVISION is bumped to 2.