Prepare switch from a64 to arm64

build/toolchain.gypi

Index: build/toolchain.gypi
diff --git a/build/toolchain.gypi b/build/toolchain.gypi
index c2a33007334a829ccab0d3bb9992628f40e091dc..539a4db4d4b4e477e1e6ae3b6ec38be0f549a12d 100644
--- a/build/toolchain.gypi
+++ b/build/toolchain.gypi
@@ -268,7 +268,7 @@
           }],  # _toolset=="target"
         ],
       }],  # v8_target_arch=="arm"
-      ['v8_target_arch=="a64"', {
+      ['v8_target_arch=="a64" or v8_target_arch=="arm64"', {
         'defines': [
           'V8_TARGET_ARCH_A64',
         ],
@@ -413,7 +413,8 @@
         ],
       }],
       ['(OS=="linux" or OS=="android") and \
-        (v8_target_arch=="x64" or v8_target_arch=="a64")', {
+        (v8_target_arch=="x64" or v8_target_arch=="a64" or \
+         v8_target_arch=="arm64")', {
         # Check whether the host compiler and target compiler support the
         # '-m64' option and set it if so.
         'target_conditions': [