Auto merge of #84665 - adamgemmell:aarch64-features, r=Amanieu

Update list of allowed aarch64 features

I recently added these features to std_detect for aarch64 linux, pending [review](https://github.com/rust-lang/stdarch/pull/1146).

I have commented any features not supported by LLVM 9, the current minimum version for Rust. Some (PAuth at least) were renamed between 9 & 12 and I've left them disabled. TME, however, is not in LLVM 9 but I've left it enabled.

See https://github.com/rust-lang/stdarch/issues/993

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -152,6 +152,12 @@ pub fn to_llvm_feature<'a>(sess: &Session, s: &'a str) -> &'a str {
         ("x86", "avx512vpclmulqdq") => "vpclmulqdq",
         ("aarch64", "fp") => "fp-armv8",
         ("aarch64", "fp16") => "fullfp16",
+        ("aarch64", "fhm") => "fp16fml",
+        ("aarch64", "rcpc2") => "rcpc-immo",
+        ("aarch64", "dpb") => "ccpp",
+        ("aarch64", "dpb2") => "ccdp",
+        ("aarch64", "frintts") => "fptoint",
+        ("aarch64", "fcma") => "complxnum",
         (_, s) => s,
     }
 }