https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89260
--- Comment #9 from ohaiziejohwahkeezuoz at xff dot cz --- The build of harfbuzz 2.3.1 with gcc 8.2.0 succeeds. I can also confirm that re-building all dependencies of harfbuzz with 8.2 branch rev268702 also succeeds. So the issue is with 8.2.1 not being able to use/read LTO objects built with 8.2.0 in some specific cases (triggered by harfbuzz C++ code for me). So if LTO object files are not supposed to be compatible between even minor gcc releases, this can be closed.
