This change is not strictly necessary, but what it does do is allow you to
add .m files (Objective-C source files) to your .cabal project.

--- ghc-6.10.2.orig/compiler/main/DriverPhases.hs	2009-03-31 06:13:15.000000000 +1300
+++ ghc-6.10.2/compiler/main/DriverPhases.hs	2009-06-18 15:54:37.000000000 +1200
@@ -156,6 +156,7 @@
 startPhase "C"        = Cc
 startPhase "cc"       = Ccpp
 startPhase "cxx"      = Ccpp
+startPhase "m"        = Cc     -- Objective-C
 startPhase "raw_s"    = Mangle
 startPhase "split_s"  = SplitMangle
 startPhase "s"        = As
@@ -195,7 +196,7 @@
 haskellish_src_suffixes      = haskellish_user_src_suffixes ++
                                [ "hspp", "hscpp", "hcr", "cmm" ]
 haskellish_suffixes          = haskellish_src_suffixes ++ ["hc", "raw_s"]
-cish_suffixes                = [ "c", "cpp", "C", "cc", "cxx", "s", "S" ]
+cish_suffixes                = [ "c", "cpp", "C", "cc", "cxx", "s", "S", "m" ]
 extcoreish_suffixes          = [ "hcr" ]
 -- Will not be deleted as temp files:
 haskellish_user_src_suffixes = [ "hs", "lhs", "hs-boot", "lhs-boot" ]
--- ghc-6.10.2.orig/compiler/main/DriverPipeline.hs	2009-03-31 06:13:16.000000000 +1300
+++ ghc-6.10.2/compiler/main/DriverPipeline.hs	2009-06-18 15:54:37.000000000 +1200
@@ -970,8 +970,10 @@
 		-- compiling .hc files, by adding the -x c option.
 		-- Also useful for plain .c files, just in case GHC saw a 
 		-- -x c option.
-			[ SysTools.Option "-x", if cc_phase `eqPhase` Ccpp
-                                                then SysTools.Option "c++" else SysTools.Option "c"] ++
+                        (if ".m" `isSuffixOf` input_fn  -- "-x c" breaks Objective-C
+                            then []
+                            else [ SysTools.Option "-x", if cc_phase `eqPhase` Ccpp
+                                                then SysTools.Option "c++" else SysTools.Option "c"]) ++
 			[ SysTools.FileOption "" input_fn
 			, SysTools.Option "-o"
 			, SysTools.FileOption "" output_fn