Add NETSDK1235 warning for non-AnyCPU PlatformTarget in modern .NET

src/Tasks/Common/Resources/Strings.resx

@@ -1014,5 +1014,9 @@ You may need to build the project on another operating system or architecture, o
     <value>NETSDK1234: RoslynCompilerType 'Framework' is deprecated and will be removed in a future version. Please refer to {0} for more information.</value>
     <comment>{StrBegins="NETSDK1234: "}{Locked="RoslynCompilerType"}{Locked="Framework"}{Locked="{0}"}</comment>
   </data>
-  <!-- The latest message added is RoslynCompilerTypeFrameworkIsDeprecated. Please update this value with each PR to catch parallel PRs both adding a new message -->
+  <data name="PlatformTargetNotRecommendedForModernDotNet" xml:space="preserve">
+    <value>NETSDK1235: Setting the PlatformTarget property to '{0}' is not recommended for modern .NET applications. The PlatformTarget property is a legacy setting from .NET Framework and has no effect in modern .NET. Consider removing PlatformTarget or setting it to 'AnyCPU'.</value>
+    <comment>{StrBegins="NETSDK1235: "}{Locked="PlatformTarget"}{Locked="AnyCPU"}</comment>
+  </data>
+  <!-- The latest message added is PlatformTargetNotRecommendedForModernDotNet. Please update this value with each PR to catch parallel PRs both adding a new message -->
 </root>