Fix build on systems where VS 2017 isn't latest on the system (#210)

- no need to get things working where VS 2019 preview is the only build available
- start using .NET Core SDK 2.1.403
  - confirmed AppVeyor and wsr-tc agents both have this SDK
- correct ordering issue with restore of System.Net.Http.Formatting.NetCore project

Author: dougbu

Runtime.msbuild

@@ -65,10 +65,14 @@
 
   <Target Name="RestorePackages" DependsOnTargets="DownloadNuGet">
     <Message Text="Restoring NuGet packages..." Importance="High" />
+
+    <!-- NuGet.exe attempts to read src\System.Net.Http.Formatting.NetCore\System.Net.Http.Formatting.NetCore.csproj and imports fails without packages. -->
+    <Exec Command='"$(NuGetExe)" restore "src\System.Net.Http.Formatting.NetCore\packages.config" -PackagesDirectory packages -NonInteractive -Verbosity quiet -ConfigFile "$(MsBuildThisFileDirectory)\.nuget\NuGet.Config"' />
+
     <Exec Command='"$(NuGetExe)" restore "%(SolutionsToBuild.Identity)" -PackagesDirectory packages -NonInteractive -Verbosity quiet -ConfigFile "$(MsBuildThisFileDirectory)\.nuget\NuGet.Config"' />
-    <!-- Pick the right Microsoft.Web.FxCop package to use and copy it to a standard location. -->
   </Target>
 
+  <!-- Pick the right Microsoft.Web.FxCop package to use and copy it to a standard location. -->
   <Target Name="BuildTools">
     <PropertyGroup>
         <FxCopProjectLocation>$(MsBuildThisFileDirectory)tools\src\Microsoft.Web.FxCop\</FxCopProjectLocation>

build.cmd

@@ -26,7 +26,7 @@ if not exist %vswhere% (
 )
 
 set InstallDir=
-for /f "usebackq tokens=*" %%i in (`%vswhere% -latest -prerelease -products * -requires Microsoft.Component.MSBuild -property installationPath`) do (
+for /f "usebackq tokens=*" %%i in (`%vswhere% -version ^[15^,16^) -latest -prerelease -products * -requires Microsoft.Component.MSBuild -property installationPath`) do (
   set InstallDir=%%i
 )
 if exist "%InstallDir%\MSBuild\15.0\Bin\MSBuild.exe" (

global.json

@@ -1,5 +1,5 @@
 {
   "sdk": {
-    "version": "2.0.0"
+    "version": "2.1.403"
   }
 }