[PATCH] [InputGraph][Gnu] Add Linkerscript support.

[Shankar Kalpathi Easwaran]

  At the time when the linkerscript node is created or parsed, it has not yet been added to the InputGraph.  For this to happen, the linkerscript node needs take InputGraph as one of the arguments, which I think would not be cleaner. Any better ways ?

  The shared library changes were needed to have all of the linkerscript changes to work, otherwise it would go in a never ending loop with a helloworld test.

  I will split this patch before I commit.

http://llvm-reviews.chandlerc.com/D2225