Update rtems_waf to support Python 3.12+

Summary

Building rtems-net-legacy with rtems_waf and python 3.12 produces these errors:

> /Volumes/Epics/LONG_ISLAND/RTEMS_FOR_EPICS/rtems-net-legacy/rtems_waf/rtems.py:639: SyntaxWarning: invalid escape sequence '.'
>   tar_rule = 'tar -cf ${TGT} --format=ustar -C ../.. $(echo "${SRC}" | sed -e 's/../..///g')'
>
> /Volumes/Epics/LONG_ISLAND/RTEMS_FOR_EPICS/rtems-net-legacy/rtems_waf/pkgconfig.py:73: SyntaxWarning: invalid escape sequence '$'
>   mre = re.compile('${[^}]+}')
> waf [commands] [options]