Fail the build if the right nugetizer nuget package cannot be deployed/packaged

This makes far easier to detect cases where the nugetizer package doesn't exist,
and later on template unfolding will fail. It won't happen for CI builds, since
the right builds happen in the right order, but it's quite easy to make this
mistake for developer builds while iterating on the extension.

Author: kzu

src/VisualStudio/NuGet.Packaging.VisualStudio.Shared.targets

@@ -18,6 +18,7 @@
 		<XmlNs>&lt;Namespace Prefix='vs' Uri='http://schemas.microsoft.com/developer/vstemplate/2005'/&gt;</XmlNs>
 	</PropertyGroup>
 
+	<!-- Embeds the NuGetizer package into the VSIX -->
 	<ItemGroup>
 		<!-- NOTE: this will only work if the solution was built at least once from the command line, 
 			 since the project reference below would have built the package in that case. -->
@@ -39,6 +40,28 @@
 		</ProjectReference>
 	</ItemGroup>
 
+	<Target Name="EnsureNuGetizerPackage" DependsOnTargets="GetVersion" BeforeTargets="DeployVsixExtensionFiles;CreateVsixContainer">
+		<ItemGroup>
+			<_NuGetizerPackage Include="$(Out)\*.nupkg" />
+			<_CurrentNuGetizerPackage Include="@(_NuGetizerPackage)"
+									  Condition="$([System.String]::New('%(Filename)').Replace('NuGet.Build.Packaging.', '')) == '$(Version)'" />
+		</ItemGroup>
+
+		<PropertyGroup>
+			<_NuGetizerPackageExists Condition="'@(_NuGetizerPackage -> Count())' != '0'">true</_NuGetizerPackageExists>
+			<_CurrentNuGetizerPackageExists Condition="'@(_CurrentNuGetizerPackage -> Count())' != '0'">true</_CurrentNuGetizerPackageExists>
+		</PropertyGroup>
+
+		<Delete Files="$(TargetPath)" Condition="'$(_NuGetizerPackageExists)' != 'true' Or '$(_CurrentNuGetizerPackageExists)' != 'true'" />
+
+		<Error Condition="'$(_NuGetizerPackageExists)' != 'true'" Text="NuGetizer nuget package was not found under '$(Out)'. 
+  Run 'build.cmd' at least once, or run 'msbuild' from the 'src\Build' folder to build the nuget package." />
+		
+		<Error Condition="'$(_CurrentNuGetizerPackageExists)' != 'true'" Text="Required NuGetizer nuget package version '$(Version)' was not found under '$(Out)'. 
+  Run 'build.cmd' at least once, or run 'msbuild' from the 'src\Build' folder to build the nuget package.
+  Packages found were: %0a@(_NuGetizerPackage -> '    %(Filename)%(Extension)', '%0a')" />
+	</Target>
+
 	<Target Name="GetVersion" DependsOnTargets="GitVersion" Returns="$(Version)">
 		<PropertyGroup>
 			<Version>$(GitSemVerMajor).$(GitSemVerMinor).$(GitSemVerPatch)</Version>

src/VisualStudio/NuGet.Packaging.VisualStudio/NuGet.Packaging.VisualStudio.csproj

@@ -84,6 +84,9 @@
     </Compile>
     <Compile Include="Views\ViewModelBase.cs" />
     <Compile Include="Wizards\MultiPlatformWizard.cs" />
+    <None Include="..\NuGet.Packaging.VisualStudio.Shared.targets">
+      <Link>NuGet.Packaging.VisualStudio.Shared.targets</Link>
+    </None>
     <None Include="NuGet.Packaging.VisualStudio.targets">
       <SubType>Designer</SubType>
     </None>