Enable outline-atomics by default on AArch64 Apple platforms

Darwin and the `-sim` targets already have a baseline with LSE. Enable
`outline-atomics` on all other Apple targets here.

Author: tgross35

compiler/rustc_target/src/spec/targets/aarch64_apple_ios.rs

@@ -16,7 +16,7 @@ pub(crate) fn target() -> Target {
             .into(),
         arch,
         options: TargetOptions {
-            features: "+neon,+fp-armv8,+apple-a7".into(),
+            features: "+neon,+fp-armv8,+apple-a7,+outline-atomics".into(),
             max_atomic_width: Some(128),
             supported_sanitizers: SanitizerSet::ADDRESS | SanitizerSet::THREAD,
             ..opts

compiler/rustc_target/src/spec/targets/aarch64_apple_tvos.rs

@@ -16,7 +16,7 @@ pub(crate) fn target() -> Target {
             .into(),
         arch,
         options: TargetOptions {
-            features: "+neon,+fp-armv8,+apple-a7".into(),
+            features: "+neon,+fp-armv8,+apple-a7,+outline-atomics".into(),
             max_atomic_width: Some(128),
             ..opts
         },

compiler/rustc_target/src/spec/targets/aarch64_apple_visionos.rs

@@ -16,7 +16,7 @@ pub(crate) fn target() -> Target {
             .into(),
         arch,
         options: TargetOptions {
-            features: "+neon,+fp-armv8,+apple-a16".into(),
+            features: "+neon,+fp-armv8,+apple-a16,+outline-atomics".into(),
             max_atomic_width: Some(128),
             supported_sanitizers: SanitizerSet::ADDRESS | SanitizerSet::THREAD,
             ..opts

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

@@ -16,7 +16,7 @@ pub(crate) fn target() -> Target {
             .into(),
         arch,
         options: TargetOptions {
-            features: "+v8a,+neon,+fp-armv8,+apple-a7".into(),
+            features: "+v8a,+neon,+fp-armv8,+apple-a7,+outline-atomics".into(),
             max_atomic_width: Some(128),
             dynamic_linking: false,
             position_independent_executables: true,