Kokoro-Windows: use latest DXC artifact

Rather than use the latest release, use the latest AppVeyor build
artifact (see
https://github.com/microsoft/DirectXShaderCompiler#downloads)

Latest release doesn't support tint's generated HLSL.

Bug: tint:872
Change-Id: Icfe5cc20647775cfae032407ae3e298c5519fbe1
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/53602
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
diff --git a/kokoro/windows/build.bat b/kokoro/windows/build.bat
index e4fe0eb..0d66287 100644
--- a/kokoro/windows/build.bat
+++ b/kokoro/windows/build.bat
@@ -62,13 +62,14 @@
 

 call :status "Fetching DXC"

 @echo on

-curl -L https://github.com/microsoft/DirectXShaderCompiler/releases/download/v1.5.2010/dxc_2020_10-22.zip --output %TEMP_DIR%\dxc.zip || goto :error

+set DXC_LATEST_ARTIFACT="https://ci.appveyor.com/api/projects/dnovillo/directxshadercompiler/artifacts/build%%2FRelease%%2Fdxc-artifacts.zip?branch=master&pr=false&job=image%%3A%%20Visual%%20Studio%%202019"

+curl -L %DXC_LATEST_ARTIFACT% --output "%TEMP_DIR%\dxc.zip" || goto :error

 @echo off

 

 call :status "Unpacking DXC"

 @echo on

 powershell.exe -Command "Expand-Archive -LiteralPath '%TEMP_DIR%\dxc.zip' -DestinationPath '%TEMP_DIR%\dxc'" || goto :error

-set PATH=%TEMP_DIR%\dxc\bin\x64;%PATH%

+set PATH=%TEMP_DIR%\dxc\bin;%PATH%

 @echo off

 

 call :status "Installing depot_tools"