Merge pull request #17323 from dotnet/wesh/FixIdentityPackageBuild

Fix identity package filtering

Author: weshaggard

src/.nuget/dir.traversal.targets

@@ -3,21 +3,28 @@
 
   <Import Project="$(MSBuildThisFileDirectory)..\..\dir.traversal.targets" />
 
-  <PropertyGroup Condition="'$(OfficialBuildId)' != ''">
-    <!-- During an official build, only build identity packages in the AllConfigurations build -->
-    <BuildIdentityPackage Condition="'$(BuildIdentityPackage)' == '' AND '$(OS)' == 'Windows_NT' AND '$(BuildArch)' == 'x64'">true</BuildIdentityPackage>
+  <PropertyGroup Condition="'$(BuildIdentityPackage)' == ''">
+    <BuildIdentityPackage>true</BuildIdentityPackage>
+
+    <!-- Used to determine if we should build some packages only once across multiple official build legs. 
+         For offline builds we still set OfficialBuildId but we need to build all the packages for a single 
+         leg only, so we also take DotNetBuildOffline into account. -->
+    <BuildingAnOfficialBuildLeg Condition="'$(OfficialBuildId)' != '' AND '$(DotNetBuildOffline)' != 'true'">true</BuildingAnOfficialBuildLeg>
+
+    <!-- During an official build, only build identity packages on windows x64 legs -->
+    <BuildIdentityPackage Condition="'$(BuildingAnOfficialBuildLeg)' == 'true' AND ('$(OS)' != 'Windows_NT' OR '$(BuildArch)' != 'x64')">false</BuildIdentityPackage>
   </PropertyGroup>
 
   <Target Name="FilterProjects" BeforeTargets="Build">
     <Error Condition="'$(PackageRID)' == ''" Text="'PackageRID' property must be specified."/>
 
     <!-- Only build packages for current RID or non-RID-specific -->
-    <ItemGroup Condition="$(BuildIdentityPackage)!='true'">
+    <ItemGroup>
       <_projectsToBuild Include="@(Project)" Condition="'%(Project.PackageTargetRuntime)' == '$(PackageRID)'" />
     </ItemGroup>
 
-    <ItemGroup Condition="$(BuildIdentityPackage)=='true'" >
-      <_projectsToBuild Include="@(Project)" Condition="'%(Project.PackageTargetRuntime)' == '$(PackageRID)' OR '%(Project.PackageTargetRuntime)' == ''" />
+    <ItemGroup Condition="'$(BuildIdentityPackage)' == 'true'">
+      <_projectsToBuild Include="@(Project)" Condition="'%(Project.PackageTargetRuntime)' == ''" />
     </ItemGroup>
 
     <ItemGroup>