… limited function on the old MACOS bash (readlink, ln, sed, and date) with a variable, and add a file (ush/bash_utils/define_macos_utilities.sh) to set these variablesappropriately for the compatible MACOS utilities if the OS is Darwin.

…owercase with custom functions that are back-compatible with MACOS

 - Add WORKFLOW_MANAGER variable for specifying machines that support rocoto (and maybe other workflow managers in the future)
 - Add run commands for specifying mpirun commands on non-rocoto machines

…all to $READLINK prior to it being defined;

…ot quit unless you manually check for non-zero exit status

…disk

…r on; setting to "2" in order to avoid divide by zero errors later on

…is capability needs more work before it is ready for showtime

…ing $SED calls here to avoid errors

…or_macos_linux

…RITE_DOPOST in ush/setup.sh

…ug_fixes_dom_20210916

Update develop for macos linux bug fixes Dom 20210916

… how these things work

…ould always be TRUE if we are in this task

Initialize `sysdir` to an empty string to avoid "unbound variable" problems