[Darwin, machopic 2/n] Compute and cache indirection rules.

[Darwin, machopic 2/n] Compute and cache indirection rules.

This caches a check for the requirement to indirect a symbol in the Darwin
ABI, and uses it where needed.  We also ensure that we place the indirection
pointers into the non-lazy symbol pointers section.  Other placements have
occurred with various platform toolchains - but these seem to have been
unintentional so we match current platform toolchains.

gcc/ChangeLog:

2019-10-08  Iain Sandoe  <iain@sandoe.co.uk>

	* config/darwin.c (machopic_indirect_data_reference): Check for
	required indirections before making direct access to defined
	values.
	(machopic_output_indirection): Place the indirected pointes for
	required indirections into the non-lazy symbol pointers section.
	(darwin_encode_section_info):
	* config/darwin.h (MACHO_SYMBOL_FLAG_MUST_INDIRECT): New.
	(MACHO_SYMBOL_MUST_INDIRECT_P): New.

From-SVN: r276708