[PATCH] Fix IA-64 build

[Roland McGrath]

I think the better solution is for those platforms not to have both modules
at all, or have one empty.  Why have two idential syscall entry points
generated?  I think you would get the right result by having an empty
lseek.[cS] in sysdeps/.../ia64 to override the unix/syscalls.list definition.
It might be handy to let syscalls.list indicate an empty module with a line
instead of adding the files. i.e.:

llseek	EXTRA	lseek	      3 __libc_lseek64 __lseek llseek __lseek64 lseek64 lseek
lseek	llseek	-

so if llseek.o is built according to the first line, then lseek.o will be
made a dummy object by the second line.