Darwin : Adjust darwin_binds_local_p for PIC code [PR100152].

Darwin : Adjust darwin_binds_local_p for PIC code [PR100152].

Darwin's dynamic linker supports interposition and lazy symbol binding.
If we are generating PIC code and a symbol is public, then it could
potentially be indirected via a lazy-resolver stub; we cannot tell at
compile-time if this will be done (since the indirection can be the
result of adding a -flat-namespace option at link-time).  Here we are
conservative and assume that any such symbol cannot bind locally.
The default implementation for binds_local_p handles undefined, weak and
common symbols which are always indirected (for mdynamic-no-pic also).

gcc/ChangeLog:

	PR target/100152
	* config/darwin.c (darwin_binds_local_p): Assume that any
	public symbol might be interposed for PIC code. Update function
	header comment to reflect current Darwin capability.