Rename "cyclone" to "apple-a7" per changes in upstream LLVM

See:
https://reviews.llvm.org/D70779
https://reviews.llvm.org/D70779#C1703593NL568

LLVM 10 merged into master at:
rust-lang#67759

Author: trevyn

src/librustc_target/spec/aarch64_apple_ios.rs

@@ -15,7 +15,7 @@ pub fn target() -> TargetResult {
         target_vendor: "apple".to_string(),
         linker_flavor: LinkerFlavor::Gcc,
         options: TargetOptions {
-            features: "+neon,+fp-armv8,+cyclone".to_string(),
+            features: "+neon,+fp-armv8,+apple-a7".to_string(),
             eliminate_frame_pointer: false,
             max_atomic_width: Some(128),
             abi_blacklist: super::arm_base::abi_blacklist(),

src/librustc_target/spec/aarch64_apple_tvos.rs

@@ -15,7 +15,7 @@ pub fn target() -> TargetResult {
         target_vendor: "apple".to_string(),
         linker_flavor: LinkerFlavor::Gcc,
         options: TargetOptions {
-            features: "+neon,+fp-armv8,+cyclone".to_string(),
+            features: "+neon,+fp-armv8,+apple-a7".to_string(),
             eliminate_frame_pointer: false,
             max_atomic_width: Some(128),
             abi_blacklist: super::arm_base::abi_blacklist(),

src/librustc_target/spec/apple_sdk_base.rs

@@ -122,7 +122,7 @@ fn target_cpu(arch: Arch) -> String {
     match arch {
         Armv7 => "cortex-a8", // iOS7 is supported on iPhone 4 and higher
         Armv7s => "cortex-a9",
-        Arm64 => "cyclone",
+        Arm64 => "apple-a7",
         I386 => "yonah",
         X86_64 => "core2",
         X86_64_macabi => "core2",