Fix clang build error in preprocessor directive
Fix clang build error in preprocessor directive

I am running into a similar issue to https://github.com/haskell/cabal/issues/1496 which was solved in https://github.com/haskell/cabal/commit/b8bf3101c0f00bd29a3e5e20755a52af57c11824 by the solution I am proposing here.
elaforge/fast-tags,elaforge/fast-tags