PR18147, relocation overflow when --unresolved-symbols=ignore-all

If ignoring unresolved symbols, ignore reloc overflows too.  If not
ignoring unresolved symbols we will report an error about the symbol
being undefined, making any report about reloc overflow superfluous.

	PR18147
	* powerpc.cc (Target_powerpc::Relocate::relocate): Don't report
	relocation errors for branches to strong undefined symbols.
2 files changed