[libraries] Restrict ILLink Suppression xml to mobile platforms (#58519)

Co-authored-by: Mitchell Hwang <mitchell.hwang@microsoft.com>

Author: mdh1418

…ink/ILLink.Suppressions.LibraryBuild.xml …ink.Suppressions.Mobile.LibraryBuild.xmlsrc/libraries/System.Net.Http/src/ILLink/ILLink.Suppressions.LibraryBuild.xml renamed to src/libraries/System.Net.Http/src/ILLink/ILLink.Suppressions.Mobile.LibraryBuild.xml src/libraries/System.Net.Http/src/ILLink/ILLink.Suppressions.LibraryBuild.xml renamed to src/libraries/System.Net.Http/src/ILLink/ILLink.Suppressions.Mobile.LibraryBuild.xml

@@ -35,6 +35,7 @@
     <ILLinkSubstitutionsXmls Include="$(ILLinkDirectory)ILLink.Substitutions.xml" />
     <ILLinkSubstitutionsXmls Condition="'$(TargetsAndroid)' == 'true' or '$(TargetsiOS)' == 'true' or '$(TargetsMacCatalyst)' == 'true' or '$(TargetsTVOS)' == 'true'"
                              Include="$(ILLinkDirectory)ILLink.Substitutions.mobile.xml" />
+    <ILLinkSuppressionsXmls Condition="'$(TargetsMobile)' == 'true'" Include="$(ILLinkDirectory)ILLink.Suppressions.Mobile.LibraryBuild.xml" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="System\Net\Http\ByteArrayContent.cs" />