RELA targets don't read initial .got.plt entries.
REL targets (ARM, x86-32) write the address of the IFUNC resolver to the
entry (write32le(buf, s.getVA())).
The default writeIgotPlt() is not meaningful. Make it a no-op. AArch64
and x86-64 will have 0 as initial .got.plt entries associated with
IFUNC.