This is makeindex, version 2.16 [TeX Live 2022] (kpathsea + Thai support).
Scanning input file basic-book-builder.idx....done (1 entries accepted, 0 rejected).
Sorting entries...done (0 comparisons).
Generating output file basic-book-builder.ind....done (5 lines written, 0 warnings).
Output written in basic-book-builder.ind.
Transcript written in basic-book-builder.ilg.