support for this has not existed since v2.0~a24-1 !!
until 4d22ca948a (v2.0~a24-1), `PROGRAM` was
defined as `PROGRAM="$(basename ${0})"`. then this commit simply got rid
of the definition.
it then flipped back and forth a bit in a few ways, but always sticking
to a simple fixed "live-build" type string after that commit, as it has
been ever since.
the code removed here has thus been junk since then, and the documentation
corrected here out of date since then.
the checking of `LB_CONFIG` is also possibly junk, but i know too little
about it. it was introduced in v1.0~a43-1 in commit
705a4178e7 with a changelog entry of
"Centraly evaluate LH_CONFIG for custom configuration file."
Gbp-Dch: Short
61aa3239c5