Improve error message when mixing 32bit and 64bit images

[morabbin]

Since we know when the user has mixed 32 and 64 bit images, let's say so in the error message. Before:

Loading object (static) dist/build/HOC_cbits.o ... ghc: dist/build/HOC_cbits.o: Bad magic. Expected: feedfacf, got: feedface.

ghc: panic! (the 'impossible' happened)
  (GHC version 7.6.1 for x86_64-apple-darwin):
        loadObj "dist/build/HOC_cbits.o": failed

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

After:

Loading object (static) dist/build/HOC_cbits.o ... ghc-stage2: Could not load image dist/build/HOC_cbits.o: bad magic!
  Expected feedfacf (64bit), got feedface (32bit).

ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.7.20130124 for x86_64-apple-darwin):
        loadObj "dist/build/HOC_cbits.o": failed

Patch to come.

[morabbin]

Patch for #7628

[simonpj]

Assigning to Ian for patch review

[andy.adamsmoran@…]

commit 12e3d3f4690d76b57ca70cdfdbad049fabd79bde

Author: Andy Adams-Moran <andy.adamsmoran@gmail.com>
Date:   Fri Jan 25 11:11:01 2013 -0800

    Patch for #7628: improve error message when mixing 32 and 64 bit images (on Mac OS X)

 rts/Linker.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

[igloo]

Applied, thanks