HP Windows installer should add mingw/bin to PATH

[nurpax]

As far as I understood, the HP installer adds GHC and other Haskell tools to PATH, like so:

$ which ghc /c/Program Files (x86)/Haskell Platform/2012.2.0.0/bin/ghc

However, it seems that the embedded mingw installation is not added to PATH. This directory is under

/c/Program Files (x86)/Haskell Platform/2012.2.0.0/mingw/bin

This by default causes installation of any package that have .c files in them to fail. Examples of such packages are at least network and direct-sqlite.

I didn't realize that mingw is included in HP so I was just assuming HP doesn't come with a C compiler at all. Thus I've been working around this by doing tricks like in https://gist.github.com/3907344#comments

I think it'd make sense for the installer to stick the mingw\bin directory to PATH just as it seems to do for ghc.

[refold]

We didn't do that previously since we didn't want to silently override the system gcc (if it's installed). Maybe the correct behaviour is to *append* $PLATFORMDIR/mingw/bin to $PATH so that the system gcc (if installed) is not overridden.

[refold]

Fixed in 2012.4.0.0 RC1.