For the NeXT 64b ABI, IVAR refs are supposed to be indirected for
Mach-O PIC. Identify them so that we can act as needed.
gcc/objc/ChangeLog:
2019-10-10 Iain Sandoe <iain@sandoe.co.uk>
* objc-next-metadata-tags.h (OCTI_RT_META_IVAR_REF): New.
(meta_ivar_ref): New.
* objc-next-runtime-abi-02.c
(next_runtime_abi_02_init_metadata_attributes): Create the
IVAR ref metadata identifier.
(ivar_offset_ref): Tag IVAR refs with specific metadata.
From-SVN: r276847
