Platform dependent search path separator

When using cabal exec on Windows, it would give an error such as:

ghc.exe: can't find a package database at
C:\Users\tchakkazulu\path\to\dir\.cabal-sandbox\i386-windows-ghc-7.6.3-packages.conf.d:C:\Program
Files (x86)\Haskell Platform\2013.2.0.0\lib\package.conf.d

(cherry picked from commit 12deea3)

Conflicts:
	cabal-install/Main.hs

cabal-install/Main.hs

@@ -140,7 +140,7 @@ import qualified Paths_cabal_install (version)
 
 import System.Environment       (getArgs, getProgName)
 import System.Exit              (exitFailure)
-import System.FilePath          (splitExtension, takeExtension)
+import System.FilePath          (splitExtension, takeExtension, searchPathSeparator)
 import System.IO                (BufferMode(LineBuffering),
                                  hSetBuffering, stdout)
 import System.Directory         (doesFileExist, getCurrentDirectory)
@@ -1046,7 +1046,8 @@ execAction execFlags extraArgs globalFlags = do
                 exitFailure
             Just ghcProg ->  do
                 g <- ghcGlobalPackageDB verbosity ghcProg
-                getEffectiveEnvironment [("GHC_PACKAGE_PATH", Just $ s ++ ":" ++ g)]
+                getEffectiveEnvironment
+                  [("GHC_PACKAGE_PATH", Just $ s ++ [searchPathSeparator] ++ g)]
 
 -- | See 'Distribution.Client.Install.withWin32SelfUpgrade' for details.
 --