[AArch64] Skip IFUNC relocations in debug sections

[AArch64] Skip IFUNC relocations in debug sections

Skip IFUNC relocations in debug sections ignored by ld.so.
Fixes the following ld test failures on aarch64:

FAIL: Build libpr18808.so
FAIL: Build libpr18808.so_2
FAIL: Run pr18808

aborting at bfd/elfnn-aarch64.c:4986 in elf64_aarch64_final_link_relocate.

bfd/
	PR ld/18808
	* elfnn-aarch64.c (elfNN_aarch64_final_link_relocate): Skip IFUNC
	relocations in debug sections, change abort to _bfd_error_handler.