[Bug lto/94311] LTO produces line info entries with invalid line numbers

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94311

--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> ---
Note we can still overflow locations so I wonder if we can have a more
forgiving failure mode?  Return UNKNOWN_LOCATION maybe.