Bump the nuget group with 1 update

Bumps Microsoft.Build from 17.12.6 to 17.12.50

---
updated-dependencies:
- dependency-name: Microsoft.Build
  dependency-version: 17.12.50
  dependency-type: direct:production
  dependency-group: nuget
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

build/_build.csproj

@@ -16,6 +16,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="Microsoft.Build" Version="17.12.50" />
     <PackageReference Include="Microsoft.Build.Tasks.Core" Version="17.14.28" />
     <PackageDownload Include="GitVersion.Tool" Version="[6.1.0]" />
   </ItemGroup>