This adds support for serveral new command line options (taken from the usage):
"-b, --bin-dir" "Override the bin installation directory [default: ${_bin_dir}]" \
"-m, --man-dir" "Override the man installation directory [default: ${_man_dir}]" \
"-a, --arch" "Override the architecture identified by the installer [default: ${_arch}]" \
"-h, --help" "Display this help message"
This also (coincidentally) allows for $BIN_DIR, $MAN_DIR, and $ARCH to be set to create default settings for these.
These variables are *always* overwritten by the command line arguments.
This diff is unusually large, as my formatter ([shfmt](https://github.com/mvdan/sh)) ran, reformatting the majority of the script.
This also adds a few utilities to the script (`log`/`abort`) and modifies `err` to simply output to stderr.
This allows for more fine grain control over script flow and output, without relying on `echo >&2`.