bpo-37238: Enable building for Windows using Visual Studio 2019 (GH-13988)

diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index 89625da..09a63c0 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -511,7 +511,7 @@
       </ClCompile>
     </ItemGroup>
   </Target>
-  <Target Name="_WarnAboutToolset" BeforeTargets="PrepareForBuild" Condition="$(PlatformToolset) != 'v140' and $(PlatformToolset) != 'v141'">
+  <Target Name="_WarnAboutToolset" BeforeTargets="PrepareForBuild" Condition="$(PlatformToolset) != 'v140' and $(PlatformToolset) != 'v141' and $(PlatformToolset) != 'v142'">
     <Warning Text="Toolset $(PlatformToolset) is not used for official builds. Your build may have errors or incompatibilities." />
   </Target>
   <Target Name="_WarnAboutZlib" BeforeTargets="PrepareForBuild" Condition="!$(IncludeExternals)">