[Workloads] Add UsingMobileWorkload property to control loading net7 packs (#77489)

Fixes #77385

Author: steveisok

src/mono/nuget/Microsoft.NET.Workload.Mono.Toolchain.Manifest/WorkloadManifest.targets.in

@@ -42,6 +42,11 @@
     <UsingBrowserRuntimeWorkload Condition="'$(UsingBrowserRuntimeWorkload)' == ''">$(WasmNativeWorkloadAvailable)</UsingBrowserRuntimeWorkload>
   </PropertyGroup>
 
+  <PropertyGroup 
+    Condition="'$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'macOS' or '$(TargetPlatformIdentifier)' == 'maccatalyst' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">
+    <UsingMobileWorkload>true</UsingMobileWorkload>
+  </PropertyGroup>
+
   <PropertyGroup Condition="'$(UsingMicrosoftNETSdkBlazorWebAssembly)' == 'true' and '$(UsingBrowserRuntimeWorkload)' == 'true'">
     <WasmGenerateAppBundle>false</WasmGenerateAppBundle>
     <UsingBlazorAOTWorkloadManifest>true</UsingBlazorAOTWorkloadManifest>

src/mono/nuget/Microsoft.NET.Workload.Mono.Toolchain.net7.Manifest/WorkloadManifest.targets.in

@@ -1,6 +1,6 @@
 <!-- Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. -->
 <Project>
-  <Import Condition="'$(TargetsNet7)' == 'true' and '$(RunAOTCompilation)' == 'true' and '$(UsingBrowserRuntimeWorkload)' == 'true'" Project="Sdk.props" Sdk="Microsoft.NET.Runtime.MonoAOTCompiler.Task.net7" />
+  <Import Condition="'$(TargetsNet7)' == 'true' and '$(RunAOTCompilation)' == 'true' and ('$(UsingBrowserRuntimeWorkload)' == 'true' or '$(UsingMobileWorkload)' == 'true')" Project="Sdk.props" Sdk="Microsoft.NET.Runtime.MonoAOTCompiler.Task.net7" />
 
   <ImportGroup Condition="'$(TargetsNet7)' == 'true' and '$(TargetPlatformIdentifier)' == 'android'">
     <Import Project="Sdk.props" Sdk="Microsoft.NET.Runtime.MonoTargets.Sdk.net7" />