Make `-dshow-available-fonts` more robust
In
https://lists.gnu.org/archive/html/bug-lilypond/2024-01/msg00005.html
it was reported that the FontConfig output might contain non-UTF8 data.
In
https://lists.gnu.org/archive/html/bug-lilypond/2024-01/msg00005.html
it was reported that the FontConfig output might contain non-UTF8 data.