Add a note about enabling profiling in haskell-platform

haskell-platform/notes.md

@@ -1,10 +1,19 @@
 You have to have haskell already installed to build this. Make sure to install
 haskell-platform-prof on Linux, not just cabal or ghc.
 
+Edit ~/.cabal/config and change
+
+    -- library-profiling: False
+
+to
+
+    library-profiling: True
+
 If you see
 
     Could not find module `Prelude'
     Perhaps you haven't installed the profiling libraries for package `base'?
     Use -v to see a list of the files searched for.
 
-try using cabal to install the package in question.
+try using cabal to install the package in question. You may need to use
+`--reinstall --force-reinstalls` to make it reinstall with profiling support.