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 12deea33d0b3c4090abe47ec5f30ae57217e10d0)

Conflicts:
	cabal-install/Main.hs