gn: Switch off neon for V8 arm simulator builds

build/config/arm.gni

Index: build/config/arm.gni
diff --git a/build/config/arm.gni b/build/config/arm.gni
index 75c5ea9d6dba81a137ca3f4cef19ec0157f97eae..6eeca62778b35a90d1630b62d57b1cd8ff23297a 100644
--- a/build/config/arm.gni
+++ b/build/config/arm.gni
@@ -25,7 +25,7 @@ if (current_cpu == "arm" || v8_current_cpu == "arm") {
     arm_tune = ""
 
     # Whether to use the neon FPU instruction set or not.
-    arm_use_neon = true
+    arm_use_neon = ""
 
     # Whether to enable optional NEON code paths.
     arm_optionally_use_neon = false
@@ -38,6 +38,15 @@ if (current_cpu == "arm" || v8_current_cpu == "arm") {
   assert(arm_float_abi == "" || arm_float_abi == "hard" ||
          arm_float_abi == "soft" || arm_float_abi == "softfp")
 
+  if (arm_use_neon == "") {
+    if (current_os == "linux" && current_cpu != v8_current_cpu) {
+      # Don't use neon on V8 simulator builds as a default.
+      arm_use_neon = false
+    } else {
+      arm_use_neon = true
+    }
+  }
+
   if (arm_version == 6) {
     arm_arch = "armv6"
     if (arm_tune != "") {