While building profiled executables with 8.2.1rc2 I've noticed the link times seem to have significantly regressed.

I don't have a minimal test case.

Testing on cabal head source tree

cabal --version
>cabal-install version 2.1.0.0
>compiled using version 2.1.0.0 of the Cabal library 
cabal new-configure --enable-profiling --enable-newer --with-ghc=/opt/ghc-8.2.1/bin/ghc
cabal build cabal-install

# hit Ctrl-C during linking
time cabal build cabal-install

gives real 1m54.833s user 1m52.936s sys 0m1.620s

doing the same with 8.0.2 links in less than a second