make install installs haddck.t files
Since changeset:55cdcc96/ghc, building GHC creates
.haddock.t files with statistics. I’m not sure how useful they are in general, but they are definitely not useful in release tarballs.
make install copies them. This affects both the binary release on the ghc page as well as distribution packages (checked Debian and Fedora).
It seems these files are used by the test suite (
testsuite/tests/perf/haddock/all.T), so probably
make install should be taught to ignore them.