Removing unneeded cpu defintion and add features analogous to netbsd/…

…freebsd

Signed-off-by: Till Wegmueller <toasterson@gmail.com>

compiler/rustc_target/src/spec/targets/aarch64_unknown_illumos.rs

@@ -3,9 +3,9 @@ use crate::spec::{base, Cc, LinkerFlavor, SanitizerSet, Target};
 pub fn target() -> Target {
     let mut base = base::illumos::opts();
     base.add_pre_link_args(LinkerFlavor::Unix(Cc::Yes), &["-std=c99"]);
-    base.cpu = "aarch64".into();
     base.max_atomic_width = Some(128);
     base.supported_sanitizers = SanitizerSet::ADDRESS | SanitizerSet::CFI;
+    base.features = "+v8a".into();
 
     Target {
         // LLVM does not currently have a separate illumos target,