Consume the VS SDK build tools and targets from NuGet

The NuGet packages for the SDK don't currently support cross-targeting,
so we must pick the right version to consume based on the version of
Visual Studio you are targeting. I implement this by simply restoring
both versions, and conditioning our MSBuild includes to the right one.
The annoying bit is since we need to restore two different versions
of the same package name via NuGet, we have to put the dependencies
in separate project.json files.

Fixes #10407.

.gitignore

@@ -34,6 +34,7 @@ UnitTestResults.html
 *.nuget.props
 *.nuget.targets
 project.lock.json
+*.project.lock.json
 
 *_i.c
 *_p.c

Restore.cmd

@@ -19,6 +19,12 @@ popd
 echo Restoring packages: Toolsets
 call %NugetExe% restore "%~dp0build\ToolsetPackages\project.json" %NuGetAdditionalCommandLineArgs% || goto :RestoreFailed
 
+echo Restoring packages: Toolsets (Dev14 VS SDK build tools)
+call %NugetExe% restore "%~dp0build\ToolsetPackages\dev14.project.json" %NuGetAdditionalCommandLineArgs% || goto :RestoreFailed
+
+echo Restoring packages: Toolsets (Dev15 VS SDK build tools)
+call %NugetExe% restore "%~dp0build\ToolsetPackages\dev15.project.json" %NuGetAdditionalCommandLineArgs% || goto :RestoreFailed
+
 echo Restoring packages: Samples
 call %NugetExe% restore "%~dp0src\Samples\Samples.sln" %NuGetAdditionalCommandLineArgs% || goto :RestoreFailed
 
@@ -29,4 +35,4 @@ exit /b 0
 
 :RestoreFailed
 echo Restore failed with ERRORLEVEL %ERRORLEVEL%
-exit /b 1
\ No newline at end of file
+exit /b 1

build/Targets/Settings.targets

@@ -81,7 +81,6 @@
     <VisualStudioReferenceAssemblyVersion Condition="'$(VisualStudioReferenceAssemblyVersion)' == ''">$(VisualStudioReferenceMajorVersion).0.0.0</VisualStudioReferenceAssemblyVersion>
     <VisualStudioCodename>Dev$(VisualStudioReferenceMajorVersion)</VisualStudioCodename>
 
-    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
     <MinimumVisualStudioVersion>$(VisualStudioVersion)</MinimumVisualStudioVersion>
 
     <VSLToolsPath Condition="'$(VSLToolsPath)' == ''">$([System.IO.Path]::GetFullPath('$(MSBuildThisFileDirectory)\..'))</VSLToolsPath>
@@ -123,6 +122,22 @@
     </Otherwise>
   </Choose>
 
+  <Choose>
+    <When Condition="'$(VisualStudioVersion)' == '15.0'">
+      <PropertyGroup>
+        <VisualStudioBuildToolsNuGetPackagePath>$(NuGetPackageRoot)\Microsoft.VSSDK.BuildTools\15.0.25201-dev15preview2</VisualStudioBuildToolsNuGetPackagePath>
+      </PropertyGroup>
+    </When>
+
+    <Otherwise>
+      <PropertyGroup>
+        <VisualStudioBuildToolsNuGetPackagePath>$(NuGetPackageRoot)\Microsoft.VSSDK.BuildTools\14.2.25201</VisualStudioBuildToolsNuGetPackagePath>
+      </PropertyGroup>
+    </Otherwise>
+  </Choose>
+
+  <Import Project="$(VisualStudioBuildToolsNuGetPackagePath)\build\Microsoft.VsSDK.BuildTools.props" Condition="'$(OS)' == 'Windows_NT'" />
+
   <!-- Build reliability -->
   <PropertyGroup>
     <OverwriteReadOnlyFiles Condition="'$(OverwriteReadOnlyFiles)' == ''">true</OverwriteReadOnlyFiles>

build/Targets/VSL.Imports.targets

@@ -271,7 +271,8 @@
 
        ==================================================================================== -->
 
-  <Import Project="$(VSToolsPath)\VSSDK\Microsoft.VsSDK.targets" Condition="'$(VSToolsPath)' != '' AND '$(ImportVSSDKTargets)' == 'true'" />
+  <Import Project="$(VisualStudioBuildToolsNuGetPackagePath)\build\Microsoft.VsSDK.BuildTools.targets" Condition="'$(ImportVSSDKTargets)' == 'true'" />
+  <Import Project="$(VSToolsPath)\VSSDK\Microsoft.VsSDK.targets" Condition="'$(ImportVSSDKTargets)' == 'true'" />
 
   <!-- ====================================================================================
 

build/ToolsetPackages/dev14.project.json

+{
+    "dependencies": {
+        "Microsoft.VSSDK.BuildTools": "14.2.25201"
+    },
+    "frameworks": {
+        "net46": {}
+    }
+}
+

build/ToolsetPackages/dev15.project.json

+{
+    "dependencies": {
+        "Microsoft.VSSDK.BuildTools": "15.0.25201-Dev15Preview2"
+    },
+    "frameworks": {
+        "net46": {}
+    }
+}
+