Build 64bit browser for Android with clang for ARMv8

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 76a42eb399d573f7fce1ad3c5897554af7ce640b..d5c157bd52cac4e2c622e082adc25caf3ed92040 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -8,7 +8,7 @@ import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/cc_wrapper.gni")
 
-if (current_cpu == "arm") {
+if (current_cpu == "arm" || current_cpu == "arm64") {
   import("//build/config/arm.gni")
 }
 if (current_cpu == "mipsel" || current_cpu == "mips64el") {
@@ -633,6 +633,9 @@ config("compiler_arm_fpu") {
   if (current_cpu == "arm" && !is_ios && !is_nacl) {
     cflags = [ "-mfpu=$arm_fpu" ]
     asmflags = cflags
+  } else if (current_cpu == "arm64" && !is_ios && !is_nacl) {
+    cflags = [ "-mcpu=$arm_fpu" ]
+    asmflags = cflags
   }
 }