Rollup merge of #112936 - Toasterson:illumos-aarch64-target, r=jackh726

Add illumos aarch64 target for rust.

This adds the newly being developed illumos aarch64 target to the rust compiler.

`@rmustacc` `@citrus-it` `@richlowe` As promissed before my hiatus :)

compiler/rustc_target/src/spec/mod.rs

@@ -1591,6 +1591,7 @@ supported_targets! {
     ("sparcv9-sun-solaris", sparcv9_sun_solaris),
 
     ("x86_64-unknown-illumos", x86_64_unknown_illumos),
+    ("aarch64-unknown-illumos", aarch64_unknown_illumos),
 
     ("x86_64-pc-windows-gnu", x86_64_pc_windows_gnu),
     ("i686-pc-windows-gnu", i686_pc_windows_gnu),

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

@@ -0,0 +1,19 @@
+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.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,
+        // so we still pass Solaris to it
+        llvm_target: "aarch64-unknown-solaris2.11".into(),
+        pointer_width: 64,
+        data_layout: "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128".into(),
+        arch: "aarch64".into(),
+        options: base,
+    }
+}

src/doc/rustc/src/platform-support.md

@@ -230,6 +230,7 @@ target | std | host | notes
 [`aarch64-unknown-nto-qnx710`](platform-support/nto-qnx.md) | ✓ |  | ARM64 QNX Neutrino 7.1 RTOS |
 `aarch64-unknown-freebsd` | ✓ | ✓ | ARM64 FreeBSD
 [`aarch64-unknown-hermit`](platform-support/hermit.md) | ✓ |  | ARM64 Hermit
+`aarch64-unknown-illumos` | ✓ | ✓ | ARM64 illumos
 `aarch64-unknown-linux-gnu_ilp32` | ✓ | ✓ | ARM64 Linux (ILP32 ABI)
 [`aarch64-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | ARM64 NetBSD
 [`aarch64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | ARM64 OpenBSD