Fix single-file build step

Author: Mike McLaughlin

eng/ci-prepare-artifacts.cmd

@@ -9,7 +9,7 @@ powershell -ExecutionPolicy ByPass -NoProfile -command "& """%~dp0common\Build.p
 if NOT '%ERRORLEVEL%' == '0' goto ExitWithCode
 
 echo Creating bundles
-powershell -ExecutionPolicy ByPass -NoProfile -command "& """%~dp0Build.ps1""" %_commonArgs% -build -bundletools -projects %~dp0..\diagnostics.sln %*"
+powershell -ExecutionPolicy ByPass -NoProfile -command "& """%~dp0Build.ps1""" %_commonArgs% -build -bundletools %*"
 if NOT '%ERRORLEVEL%' == '0' goto ExitWithCode
 
 echo Creating dbgshim packages