Add build hook to AccountDeleter and GitHubVulnerabilities2Db (#7973)

Progress on NuGet/Engineering#2891

Author: joelverhagen

src/AccountDeleter/AccountDeleter.csproj

@@ -125,4 +125,5 @@
   </PropertyGroup>
   <Import Project="$(SignPath)\sign.targets" Condition="Exists('$(SignPath)\sign.targets')" />
   <Import Project="$(SignPath)\sign.microbuild.targets" Condition="Exists('$(SignPath)\sign.microbuild.targets')" />
+  <Import Project="$(NuGetBuildExtensions)" Condition="'$(NuGetBuildExtensions)' != '' And Exists('$(NuGetBuildExtensions)')" />
 </Project>

src/GitHubVulnerabilities2Db/GitHubVulnerabilities2Db.csproj

@@ -118,4 +118,5 @@
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <Import Project="$(SignPath)\sign.targets" Condition="Exists('$(SignPath)\sign.targets')" />
   <Import Project="$(SignPath)\sign.microbuild.targets" Condition="Exists('$(SignPath)\sign.microbuild.targets')" />
+  <Import Project="$(NuGetBuildExtensions)" Condition="'$(NuGetBuildExtensions)' != '' And Exists('$(NuGetBuildExtensions)')" />
 </Project>