[JITLINK] Disable ELF_ppc64_relocations.s on SystemZ host (#168939)
Mark ELF_ppc64_relocations.s as unsupported on SystemZ because of cross
build issue related to using dlsym for host symbols.
Test fails to resolve __tls_get_aadr on SystemZ host.
Co-authored-by: anoopkg6 <anoopkg6@github.com>