Unfortunately, our E2E tests use custom LIT format so I wasn't able to
make `llvm-lit` generate the results into a JSON file. That meant that I
have to redirect the entire output into a log file and Github Actions
won't be able to show intermediate progress until `llvm-lit` finishes
execution.

Another thing worth mentioning is that these summaries aren't
"searchable" via Github's search queries (unlike comments), but I think
it's still a usability improvement because it would allow to see all the
failures on a single page.