More CPP usage fixes

Cabal/Distribution/Compat/CreatePipe.hs

@@ -23,7 +23,7 @@ import GHC.IO.FD (mkFD)
 import GHC.IO.Device (IODeviceType(Stream))
 import GHC.IO.Handle.FD (mkHandleFromFD)
 import System.IO (IOMode(ReadMode, WriteMode))
-#elif ghcjs_HOST_OS
+#elif defined ghcjs_HOST_OS
 #else
 import System.Posix.IO (fdToHandle)
 import qualified System.Posix.IO as Posix
@@ -60,7 +60,7 @@ foreign import ccall "io.h _pipe" c__pipe ::
 
 foreign import ccall "io.h _close" c__close ::
     CInt -> Prelude.IO CInt
-#elif ghcjs_HOST_OS
+#elif defined ghcjs_HOST_OS
 createPipe = error "createPipe"
   where
     _ = callStack