Resolve unknown platform name warnings (#50193)

* Add targets as supported platforms

* Update analyzer version

* Update comment, remove '' != 'false' condition

eng/Versions.props

@@ -45,7 +45,7 @@
     <ProjectServicingConfiguration Include="Microsoft.NETCore.App.Ref" PatchVersion="0" />
   </ItemGroup>
   <PropertyGroup>
-    <MicrosoftCodeAnalysisNetAnalyzersVersion>6.0.0-preview3.21158.1</MicrosoftCodeAnalysisNetAnalyzersVersion>
+    <MicrosoftCodeAnalysisNetAnalyzersVersion>6.0.0-preview3.21168.1</MicrosoftCodeAnalysisNetAnalyzersVersion>
     <MicrosoftCodeAnalysisCSharpCodeStyleVersion>3.9.0-5.final</MicrosoftCodeAnalysisCSharpCodeStyleVersion>
     <MicrosoftCodeAnalysisCSharpVersion>3.9.0-5.final</MicrosoftCodeAnalysisCSharpVersion>
     <!-- Arcade dependencies -->

eng/targetframeworksuffix.props

@@ -9,6 +9,8 @@
     <TargetPlatformIdentifier>$(TargetFrameworkSuffix)</TargetPlatformIdentifier>
     <TargetPlatformVersion>1.0</TargetPlatformVersion>
     <TargetPlatformMoniker>$(TargetFrameworkSuffix),Version=$(TargetPlatformVersion)</TargetPlatformMoniker>
+    <!-- Value of 0.0 produces versionless SupportedOSPlatform attribute, which is important for platforms not expected to have a version -->
+    <SupportedOSPlatformVersion>0.0</SupportedOSPlatformVersion>
   </PropertyGroup>
   
   <Choose>

eng/versioning.targets

@@ -47,17 +47,27 @@
   <ItemGroup Condition="('$(TargetsBrowser)' == 'true' or '$(CrossPlatformAndHasNoBrowserTarget)' == 'true') and '$(IsTestProject)' != 'true'">
     <SupportedPlatform Include="browser"/>
   </ItemGroup>
-
-  <!-- Enables warnings for tvOS targeted builds -->
-  <ItemGroup Condition="'$(TargetstvOS)' == 'true' and '$(IsTestProject)' != 'true'">
-    <SupportedPlatform Include="tvos"/>
+  
+  <!-- Add target platforms into MSBuild SupportedPlatform list -->
+  <ItemGroup Condition="'$(TargetsAnyOS)' != 'true' and '$(IsTestProject)' != 'true'">
+    <SupportedPlatform Condition="'$(Targetsillumos)' == 'true'" Include="illumos"/>
+    <SupportedPlatform Condition="'$(TargetsSolaris)' == 'true'" Include="Solaris"/>
+    <SupportedPlatform Condition="'$(TargetstvOS)' == 'true'" Include="tvOS"/>
+    <SupportedPlatform Condition="'$(TargetsUnix)' == 'true'" Include="Unix"/>
   </ItemGroup>
 
   <ItemGroup>
     <_unsupportedOSPlatforms Include="$(UnsupportedOSPlatforms)" />
   </ItemGroup>
 
-  <Target Name="AddUnsupportedOSPlatformAttribute" BeforeTargets="GenerateAssemblyInfo" AfterTargets="PrepareForBuild" Condition="'@(_unsupportedOSPlatforms)' != '' and '$(IsTestProject)' != 'true' and '$(IncludePlatformAttributes)' != 'false'">
+  <!-- Adds UnsupportedOSPlatform attribute to the assembly when:
+      * At least one <UnsupportedOSPlatforms /> has been specified
+      * This isn't a test project
+      * This is a cross-platform target
+      * The build isn't targeting .NET Framework
+    -->
+  <Target Name="AddUnsupportedOSPlatformAttribute" BeforeTargets="GenerateAssemblyInfo" AfterTargets="PrepareForBuild"
+    Condition="'@(_unsupportedOSPlatforms)' != '' and '$(TargetsAnyOS)' == 'true' and '$(IsTestProject)' != 'true' and '$(TargetFrameworkIdentifier)' != '.NETFramework'">
     <ItemGroup>
       <AssemblyAttribute Include="System.Runtime.Versioning.UnsupportedOSPlatform">
         <_Parameter1>%(_unsupportedOSPlatforms.Identity)</_Parameter1>

src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/CounterGroup.cs

@@ -15,7 +15,9 @@ namespace Microsoft.Diagnostics.Tracing
 namespace System.Diagnostics.Tracing
 #endif
 {
+#if NETCOREAPP
     [UnsupportedOSPlatform("browser")]
+#endif
     internal sealed class CounterGroup
     {
         private readonly EventSource _eventSource;

src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/DiagnosticCounter.cs

@@ -20,7 +20,9 @@ namespace System.Diagnostics.Tracing
     /// DiagnosticCounter is an abstract class that serves as the parent class for various Counter* classes,
     /// namely EventCounter, PollingCounter, IncrementingEventCounter, and IncrementingPollingCounter.
     /// </summary>
+#if NETCOREAPP
     [UnsupportedOSPlatform("browser")]
+#endif
     public abstract class DiagnosticCounter : IDisposable
     {
         /// <summary>

src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventCounter.cs

@@ -24,7 +24,9 @@ namespace System.Diagnostics.Tracing
     /// See https://github.com/dotnet/runtime/blob/main/src/libraries/System.Diagnostics.Tracing/tests/BasicEventSourceTest/TestEventCounter.cs
     /// which shows tests, which are also useful in seeing actual use.
     /// </summary>
+#if NETCOREAPP
     [UnsupportedOSPlatform("browser")]
+#endif
     public partial class EventCounter : DiagnosticCounter
     {
         /// <summary>