fontenc package needs special handling

[kmccurley]

I am having a hard time understanding it, but apparently there is a blanket recommendation not to use the fontenc package in lualatex, but rather to use fontspec. There is a complicated discussion that points out it's possible to load fontenc multiple times with different character encodings for the output. I think our best bet is to make sure that \usepackage[T1]{fontenc} does not appear in main.tex, because I don't think you can prevent fontenc from being loaded otherwise. Maybe \AtBeginDocument can check if fontenc is loaded and complain in iacrcc.cls, but we would need some tests for this.