Extend unhappy workaround for bytestring-lexing

Extends the workaround for `bytestring-lexing` which has a build-tool dependency on `alex`.

(In our cut-down version of Yesod we don't depend on any of `language-javascript` `haskell-src-exts` `pandoc`, but we do depend on `hedis` which in turn uses `bytestring-lexing`.)