Update README

Author: gbaz

README

@@ -12,6 +12,8 @@ foundation on which to base production software.
 While end-users _can_ build the platform themselves, it is generally recommended,
 if possible, to use the prebuilt binaries available from https://www.haskell.org/platform/
 
+The platform distribution and tooling are more intended instead for those wishing to package a platform installer for use by others.
+
 DISTRIBUTION
 ------------
 The platform comes in several forms:
@@ -29,7 +31,7 @@ Development usually happens in other branches.
 includes the sources of the packages that make up the platform, and excludes
 some of the ancillary things in the source repo. You can use this to build
 the platform without access to hackage or even an internet connection. You still
-need a GHC bindist.
+need a GHC bindist, as well as cabal and stack binaries, either built from source or available from their respective websites.
 
 *installer* - For Windows and OS X, the platform is distributed as a standard
 installer for the operating system. It contains a fully built version of the
@@ -73,12 +75,15 @@ installer packages.
 
 In either the source repo or unpacked source tarball, simply run this:
 
-   ./platform.sh $PATH_TO_GHC_BINDIST_TARBALL
+   ./platform.sh $PATH_TO_GHC_BINDIST_TARBALL  $PATH_TO_CABAL_EXECUTABLE $PATH_TO_STACK_EXECUTABLE
 
 This will build the hptool itself, and then use that tool to build first the
 platform source tarball, and finally the hermetic build of all the platform
 packages.
 
+By default this now builds a "minimal" installer that does not install libraries beyond core. To build a "full" installer 
+with a broader range of libraries pre-installed in the global store, pass a "-f" option.
+
 If you are building for a Posix like system (Linux, or BSD), then you can add
 the command line option --prefix to specify where, on the target system the
 tree of built things will be placed. It defaults to "/usr/local/haskell".  The