Harfbuzz needs the latest version of Freetype – I’ve added this to the CI build. This is again a standard ./autogen.sh ./configure make make install build.
Upgrading to the latest freetype fixes the harfbuzz build but breaks the octave build – fontconfig is still using the original freetype installed by yum, in /usr/ rather than the newly built one in /usr/local. Rebuilding fontconfig resolves this problem but causes the fltk build to fail. Setting fltk to look for the fontconfig.pc file in /usr/local/lib/pkgconfig resolves this.