[PATCH] XCore target -fexceptions flag handling

[robert lytton]

  Hi Eric,

  >Why use this instead of just setting the exceptions enabled by default flag to false otherwise?

  Are you thinking along the lines of the original patch [[ http://llvm-reviews.chandlerc.com/differential/diff/6509/ | 6509 ]]?
  The original patch decided upon whether exceptions were enabled differently for the compiler's and linker's input.
  This refactors the decision into one place.

  > I imagine there's another test for the default behavior on some other platforms, but could you verify?

  The default behavior is tested in test/Driver/clang-exception-flags.cpp

  Thank you
  Robert

http://llvm-reviews.chandlerc.com/D2570