[ELF] Fix DT_INIT_ARRAY{SZ} and DT_FINI_ARRAY{SZ}

The dynamic table was creating the entry DT_FINI_ARRAY{SZ} even when there was
no .fini_array section. The entries should be creating in the dynamic section
only if there are sections .init_array/.fini_array in the output.

Fixes the tests that checked for errroneous outputs.

llvm-svn: 221588