Imported Upstream version 5.2.0.175

Former-commit-id: bb0468d0f257ff100aa895eb5fe583fb5dfbf900

external/corefx/run.cmd

@@ -1,12 +1,30 @@
 @if not defined _echo @echo off
 setlocal
 
+:: Default to highest Visual Studio version available
+::
+:: For VS2015 (and prior), only a single instance is allowed to be installed on a box
+:: and VS140COMNTOOLS is set as a global environment variable by the installer. This
+:: allows users to locate where the instance of VS2015 is installed.
+::
+:: For VS2017, multiple instances can be installed on the same box SxS and VS150COMNTOOLS
+:: is no longer set as a global environment variable and is instead only set if the user
+:: has launched the VS2017 Developer Command Prompt.
+::
+:: Following this logic, we will default to the VS2017 toolset if VS150COMNTOOLS tools is
+:: set, as this indicates the user is running from the VS2017 Developer Command Prompt and
+:: is already configured to use that toolset. Otherwise, we will fallback to using the VS2015
+:: toolset if it is installed. Finally, we will fail the script if no supported VS instance
+:: can be found.
 if not defined VisualStudioVersion (
-  if defined VS140COMNTOOLS (
+  if defined VS150COMNTOOLS (
+    call "%VS150COMNTOOLS%\VsDevCmd.bat"
+    goto :Run
+  ) else if defined VS140COMNTOOLS (
     call "%VS140COMNTOOLS%\VsDevCmd.bat"
     goto :Run
   )
-  echo Error: Visual Studio 2015 required.
+  echo Error: Visual Studio 2015 or 2017 required.
   echo        Please see https://github.com/dotnet/corefx/blob/master/Documentation/project-docs/developer-guide.md for build instructions.
   exit /b 1
 )
@@ -20,6 +38,9 @@ set Platform=
 call %~dp0init-tools.cmd
 if NOT [%ERRORLEVEL%]==[0] exit /b 1
 
+:: Always copy over the Tools-Override
+xcopy %~dp0Tools-Override\* %~dp0Tools /y >nul
+
 set _toolRuntime=%~dp0Tools
 set _dotnet=%_toolRuntime%\dotnetcli\dotnet.exe