GHCi staggers to its feet on x86_64.

The problem is that in the small code model on x86_64, all symbol
relocations are 32-bit, because the program is assumed to fit into
2Gb.  However, shared libraries are linked outside the 2Gb range, and
the linker arranges that references to shared library symbols either
go via a jump table (for code references) or are copied into the 2Gb
area (for data references).

In GHCi's linker, We can use a jump table for the function symbols,
but we can't copy the data symbols because they've already been
relocated to point to the shared library.  What's more, we can't tell
whether a symbol reference is to code or data - this information is
only available from the shared library itself.

Fortunately, at least HSbase.o doesn't have any data references to
shared libraries (at least on the Linux distro I'm using), so I can at
least get GHCi up and limping.