PowerPC gold assertion on missing global entry stub

PowerPC gold assertion on missing global entry stub

Global entry stubs are used on ELFv2 to provide addresses for
functions not defined in a non-PIC executable but whose address is
taken, in much the same way as PLT stub code is used on other
targets to provide function addresses.  We don't want to insert a
global entry stub just because (bogus) debug info refers to the
address of a non-local function, but we also don't want gold to die.

	* powerpc.cc (Target_powerpc::Relocate::relocate): Don't assert
	on missing global entry stub due to bogus debug info.