Use SDK msbuild to build wrappers

On windows, the use of run.exe, config.json, and msbuild.cmd uses
msbuild.exe on the path. This change will build wrappers using the
local SDK via "dotnet msbuild", bypassing run.exe. Run.exe will go
away entirely with the move from buildtools to arcade, so other build
invocatios should follow suit.

build-test.cmd

@@ -113,6 +113,8 @@ if defined __BuildAgainstPackagesArg (
 @if defined _echo @echo on
 
 set __RunArgs=-BuildOS=%__BuildOS% -BuildType=%__BuildType% -BuildArch=%__BuildArch%
+REM As we move from buildtools to arcade, __RunArgs should be replaced with __msbuildArgs
+set __msbuildArgs=/p:__BuildOS=%__BuildOS% /p:__BuildType=%__BuildType% /p:__BuildArch=%__BuildArch%
 
 if defined __ToolsetDir (
     rem arm64 builds currently use private toolset which has not been released yet
@@ -156,6 +158,12 @@ REM ===
 REM =========================================================================================
 call "%__ProjectDir%\init-tools.cmd"
 @if defined _echo @echo on
+set "__ToolsDir=%__ProjectDir%\Tools"
+set "__DotnetHost=%__ToolsDir%\dotnetcli\dotnet.exe"
+if not exist "%__DotnetHost%" (
+   echo %__DotnetHost% not found after init-tools.
+   exit /b 1
+)
 
 REM =========================================================================================
 REM ===
@@ -424,7 +432,8 @@ set __msbuildLog=/flp:Verbosity=normal;LogFile="%__BuildLog%"
 set __msbuildWrn=/flp1:WarningsOnly;LogFile="%__BuildWrn%"
 set __msbuildErr=/flp2:ErrorsOnly;LogFile="%__BuildErr%"
 
-call %__ProjectDir%\run.cmd build -Project=%__ProjectDir%\tests\runtest.proj -BuildWrappers -MsBuildEventLogging=" " -MsBuildLog=!__msbuildLog! -MsBuildWrn=!__msbuildWrn! -MsBuildErr=!__msbuildErr! %__RunArgs% %__BuildAgainstPackagesArg% %TargetsWindowsArg% %__unprocessedBuildArgs%
+REM Build wrappers using the local SDK's msbuild. As we move to arcade, the other builds should be moved away from run.exe as well.
+call %__DotnetHost% msbuild %__ProjectDir%\tests\runtest.proj /p:BuildWrappers=true !__msbuildLog! !__msbuildWrn! !__msbuildErr! %__msbuildArgs% %__unprocessedBuildArgs%
 if errorlevel 1 (
     echo Xunit Wrapper build failed
     exit /b 1