Decide whether to accept libstdc++ dependency in GHC binary distributions

With the merge of text-2.0, GHC's binary distributions now depend upon libstdc++ due to https://gitlab.haskell.org/ghc/packages/text/-/blob/master/simdutf/simdutf.cpp. Even prior to merge I was a bit worried about the trouble that this might cause for downstream users and packagers. Unfortunately, it has already started to cause trouble, with head.hackage builds failing due to https://github.com/mpickering/ghc-artefact-nix/issues/13.

text's dependency on simdjson can be disabled using the simdjson Cabal flag. Perhaps we should consider doing this in GHC builds? On one hand, this simplifies packaging. On the other, this means that a significant fraction of the ecosystem won't benefit from the improved validation performance offered by simdjson since the text package is tied to that used by ghc in any install plan including the ghc package.