This R package relies on Cargo, the Rust package manager. Cargo can be provided in a number of ways.
Either of the following methods should work (although the first method will guarantee that the most
recent version is installed):

1. Install from https://rustup.rs, an official Rust website, e.g.:

   Linux / MacOS:
   * Run: curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- --no-modify-path -y

   Windows:
   * Download rustup-init.exe from https://rustup.rs
   * Open the terminal in the directory in which rustup-init.exe was downloaded
   * Run: .\rustup-init.exe --no-modify-path -y --default-host x86_64-pc-windows-gnu

   If you do not mind having the script modify your PATH environment variable, remove the
   "--no-modify-path" argument. Having Cargo's bin directory in your PATH environment variable is
   *not* necessarily, however, as the R package will still be able to find the 'cargo' executable
   in the $HOME/.cargo/bin directory.

OR

2. Install from a package manager and let 'cargo' by found using the $PATH environment variable,
   e.g.:

   Debian:  sudo apt install cargo
   Ubuntu:  sudo apt install cargo
   Fedora:  sudo dnf install cargo

   Note that package managers for MacOS and Windows are *not* recommended.  Homebrew's Rust
   may yield static libraries with a higher minimum macOS version than that used by the compiler
   for R.  Likewise Msys2 may be unsuitable since, "One should only be installing packages from
   'msys' sub-repository of Msys2, mixing other sub-repositories with the toolchain may cause
   trouble." (https://cran.r-project.org/bin/windows/base/howto-R-devel.html)

