COMP: removed '-read_only_relocs suppress' linker option on Mac

This flag can only be used on i386;
it cannot be used on x86_64
(the current architucture) and emits
a linker warning.  From what I can
tell, it's only there as an
optimization and not required for
correctness, so I've just removed
it unconditionally since trying to
do architecture checks would be
hard, especially with universal
binaries, etc.

Change-Id: I89da175526e130f94cec282090322c2bf0f748ab
Merge topic 'read_only_relocs' into master

e694d5f5 COMP: removed '-read_only_relocs suppress' linker option on Mac