Cabal and cross compilation

Hey, I am working on getting ghc to cross compile to android. When trying to get haskeline to compile. I want to change the cabal file such that it sets a flag when compiling for android. For that I changed cabal so that it recognizes android as a OS. But cabal seems to get its os information from System.Info.os, and from what I can tell this always returns the host os and not the target os. Am I getting this right, is cabal unaware of the target os? How can we change this? Regards, Nathan