Log Message:
Upgrade to rust version 1.44.1.

Pkgsrc changes:
 * None.

Upstream changes:

Version 1.44.1 (2020-06-18)
===========================

* [rustfmt accepts rustfmt_skip in cfg_attr again.][73078]
* [Don't hash executable filenames on apple platforms, fixing backtraces.]
  [cargo/8329]
* [Fix crashes when finding backtrace on macOS.][71397]
* [Clippy applies lint levels into different files.][clippy/5356]

[71397]: https://github.com/rust-lang/rust/issues/71397
[73078]: https://github.com/rust-lang/rust/issues/73078
[cargo/8329]: https://github.com/rust-lang/cargo/pull/8329
[clippy/5356]: https://github.com/rust-lang/rust-clippy/issues/5356