rust16 installs a limited set of rust binaries to /opt/rust16. This is
to allow rust-based SlackBuilds to build more recent versions than
would be possible with system rust.

To use the rust16 binaries in a SlackBuild, make the following export
statements:

export PATH="/opt/rust16/bin:$PATH"
if [ -z "$LD_LIBRARY_PATH" ]; then
  export LD_LIBRARY_PATH="/opt/rust16/lib$LIBDIRSUFFIX"
else
  export LD_LIBRARY_PATH="/opt/rust16/lib$LIBDIRSUFFIX:$LD_LIBRARY_PATH"
fi

If your SlackBuild experiences build failures on 64-bit systems, please
ensure that the LIBDIRSUFFIX variable is set.

rust16 is not intended as a substitute for rustup or for the Slackware
rust package in terms of rust development purposes.

Separate downloads are available for i686 and x86_64. -current users may
be able to ignore rust16 as a dependency for some packages.