mkcheck.in partial patch for AIX

[David Edelsohn]

>>>>> Alexandre Oliva writes:

>> Yes, but this is somewhat C++-specific.  Linking every -static
>> program against libiconv.a seems a bit much.

Alexandre> I thought it was a non-shared library that would be discarded unless
Alexandre> some symbol was imported from it.  Isn't that the case?

	libiconv.a is a shared library.  I apparently is implicitly
re-exported by libc.a when linking shared, but needs to be referenced
explicitly when linking static.  Possibilities include defining it in
LINK_SPEC or in MATH_LIBRARY used by g++spec.c.

David