utils: enable a summary view on the toolchain build on Windows

This should help us understand where our build time is being spent.
Hopefully we can use this information to properly identify places to
reduce the cost of a build.

Author: compnerd

utils/build-windows-toolchain.bat

@@ -77,7 +77,8 @@ powershell.exe -ExecutionPolicy RemoteSigned -File %~dp0build.ps1 ^
   -ImageRoot %BuildRoot% ^
   %SkipPackagingArg% ^
   %TestArg% ^
-  -Stage %PackageRoot% || (exit /b 1)
+  -Stage %PackageRoot% ^
+  -Summary || (exit /b 1)
 
 :: Clean up the module cache
 rd /s /q %LocalAppData%\clang\ModuleCache