Add armv8 support for 32-bit building

build/config/arm.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # These are primarily relevant in current_cpu == "arm" contexts, where
 # ARM code is being compiled.  But they can also be relevant in the
 # host toolchain context when target_cpu == "arm", where a host-side
 # build tool being built will change its behavior depending on the
 # details of the target configuration.
 if (target_cpu == "arm" || current_cpu == "arm") {
@@ skipping 49 matching lines @@
       }
     }
 
     arm_use_thumb = true
 
     if (arm_use_neon) {
       arm_fpu = "neon"
     } else {
       arm_fpu = "vfpv3-d16"
     }
+  } else if (arm_version == 8) {
+    arm_arch = "armv8-a"
+    if (arm_tune == "") {
+      arm_tune = "generic-armv8-a"
+    }
+
+    if (arm_float_abi == "") {
+      if (is_android) {
+        arm_float_abi = "softfp"
+      } else {
+        arm_float_abi = "hard"
+      }
+    }
+
+    arm_use_thumb = true
+
+    if (arm_use_neon) {
+      arm_fpu = "neon"
+    } else {
+      arm_fpu = "vfpv3-d16"
+    }
   }
 } else if (current_cpu == "arm64") {
   # arm64 supports only "hard".
   arm_float_abi = "hard"
 }