Build DXC on Win Arm64

Fixed: dawn:2446
Change-Id: Ia90ab09abc0354fbbcc1744bc20c9de029b8339f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/185242
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Austin Eng <enga@chromium.org>

BUILD.gn

@@ -62,7 +62,8 @@ group("cmds") {
     "src/dawn/samples",
     "src/tint:cmds",
   ]
-  if (target_cpu == "x64" && (is_win || is_linux || is_mac)) {
+  if ((target_cpu == "x64" && (is_win || is_linux || is_mac)) ||
+      (target_cpu == "arm64" && is_win)) {
     deps += [ "third_party/gn/dxc:dxc" ]
   }
 }

scripts/dawn_features.gni

@@ -55,10 +55,9 @@ declare_args() {
   dawn_use_swiftshader = !is_android && !is_ios
 
   # Whether we allow building DXC.
-  # DXC requires SM6.0+ which is blocklisted on x86,
-  # and arm64 support is not implemented yet.
+  # DXC requires SM6.0+ which is blocklisted on x86.
   # See crbug.com/tint/1753.
-  dawn_use_built_dxc = is_win && target_cpu != "x86" && target_cpu != "arm64"
+  dawn_use_built_dxc = is_win && target_cpu != "x86"
 }
 
 declare_args() {