the cause of PR41260 is new additional epilog unwind information

[Jack Howarth]

   FYI, to clarify for others who haven't been following
PR41260, the messages...

http://lists.cs.uiuc.edu/pipermail/llvmdev/2009-September/025894.html
http://lists.cs.uiuc.edu/pipermail/llvmdev/2009-September/025898.html

explain the changes in libgcc handling as of darwin10. If I
understand those correctly, the symbols exported through any
libgcc_s.10.5 are now provided from libSystem. This means
that we aren't really using the FSF libgcc unwinder code but
that from unwinder in libSystem. In Darwin10, this behavior
occurs no matter the order -lSystem and -lgcc on the link
line. Only additional symbols not contained in libgcc_s.10.5
will be used from libgcc_s.
           Jack