Issues with fontforge appimage when building proton

I have been trying to build Proton 7.0-4 on Ubuntu 18.04 but I ran into a problem I thought should be raised here around fontforge.

I initially had a version of fontforge from 2017 since that was the only one available in apt for Ubuntu 18.04, however this was not compatible due to it not supporting SFD 3.2. I went to the fontforge GitHub repo directly and downloaded the latest AppImage, the only way they now distribute them, and received errors that files were not found during the proton build process. I found that since they moved to using AppImages they no longer support relative paths for scripts, see here.

I am currently trying again on Ubuntu 20.04 to see if the 2019 fontforge on apt works instead. I will update with my progress later if there is anything to note.

Just wanted to raise this since it may become more difficult for people to build proton with the fontforge AppImage requiring absolute paths, and new versions of fontforge will be AppImage only it seems.

Here is the affected code: Makefile.in

Start with Makefile.in around line 966 and reproduce the Proton 7.0-4 build on Ubuntu using the available fontforge versions. Compare the Ubuntu 18.04 package with the fontforge AppImage and trace the missing-file errors during the build. Done means the Proton build completes without the fontforge path-related failures.