LTO: Handle __real_SYM reference in IR

LTO: Handle __real_SYM reference in IR

When an IR symbol SYM is referenced in IR via __real_SYM, its resolution
should be LDPR_PREVAILING_DEF, not PREVAILING_DEF_IRONLY, since LTO
doesn't know that __real_SYM should be resolved by SYM.

bfd/

	PR ld/29086
	* linker.c (bfd_wrapped_link_hash_lookup): Mark SYM is referenced
	via __real_SYM.

include/

	PR ld/29086
	* bfdlink.h (bfd_link_hash_entry): Add ref_real.

ld/

	PR ld/29086
	* plugin.c (get_symbols): Resolve SYM definition to
	LDPR_PREVAILING_DEF for __real_SYM reference.
	* testsuite/ld-plugin/lto.exp: Run PR ld/29086 test.
	* testsuite/ld-plugin/pr29086.c: New file.