[cpu] Do not set jscvt on iOS

On old iPhones, jscvt is not availale. This CL diables jscvt on iOS in
general.

R=tebbi@chromium.org

Bug: v8:13004
Change-Id: Ib2651d7fa43892c06dc8c36e497a8c76344b5051
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3726297Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81462}

src/base/cpu.cc

@@ -785,8 +785,9 @@ CPU::CPU()
     has_jscvt_ = HasListItem(features, "jscvt");
     delete[] features;
   }
-#elif V8_OS_DARWIN
+#elif V8_OS_DARWIN && !V8_OS_IOS
   // ARM64 Macs always have JSCVT.
+  // TODO(v8:13004): Detect if an iPhone is new enough to support jscvt.
   has_jscvt_ = true;
 #endif  // V8_OS_WIN
 

src/codegen/arm64/assembler-arm64.cc

@@ -73,7 +73,8 @@ constexpr unsigned CpuFeaturesFromCompiler() {
 
 constexpr unsigned CpuFeaturesFromTargetOS() {
   unsigned features = 0;
-#if defined(V8_TARGET_OS_MACOS)
+#if defined(V8_TARGET_OS_MACOS) && !defined(V8_TARGET_OS_IOS)
+  // TODO(v8:13004): Detect if an iPhone is new enough to support jscvt.
   features |= 1u << JSCVT;
 #endif
   return features;