libiberty, Darwin : Fix simple-object LTO table for cross-endian case.

We encapsulate streamed IR in three special sections with a table
that describes their entries.  The table is expected to be written
with native endianness for the target, but for cross-endian cross-
compilation the swapping was omitted.  Fixed thus.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

libiberty/ChangeLog:

	* simple-object-mach-o.c (simple_object_mach_o_write_segment):
	Arrange to swap the LTO index tables where needed.