Draft: EventLoop Boost Fix, main branch (2023.07.14.)

gt_SubmitDirManager.cxx uses <boost/filesystem.hpp>, so we need to use that Boost component explicitly.

I came across this issue while building AnalysisBase on x86_64-el9-gcc11-opt, while testing a fix (atlasexternals!1032 (merged)) for !64280 (merged). I was so ready to blame @averbyts's !64255 (merged) update when I saw the failure because of boost::filesystem, but of course that had nothing to do with it. The reason I bring it up is that while I wanted to open this MR, it may be the best idea to just wait for !64255 (merged) to be swept into main, as that will actually be a nicer fix for this issue. Still wanted to open this to keep track of things...