Fix name error in aarch64_apple_watchos tier 3 target

Author: leohowell

compiler/rustc_target/src/spec/targets/aarch64_apple_watchos.rs

@@ -4,7 +4,7 @@ use crate::spec::{Target, TargetOptions};
 pub fn target() -> Target {
     let base = opts("watchos", Arch::Arm64);
     Target {
-        llvm_target: "aarch-apple-watchos".into(),
+        llvm_target: "aarch64-apple-watchos".into(),
         pointer_width: 64,
         data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
         arch: "aarch64".into(),