Temporarily disable API checks in all x-plat runs

Author: dougbu

src/Internal.AspNetCore.Sdk/targets/ApiCheck.props

@@ -5,6 +5,9 @@
 <Project>
   <!-- Set nothing if handled in project file or already done in outer build. -->
   <PropertyGroup>
+    <!-- Temporarily disable API checks in all x-plat runs. Universe builds fail at FileSystem repo. -->
+    <EnableApiCheck Condition=" '$(OS)' != 'Windows_NT' ">false</EnableApiCheck>
+
     <!-- Unconditionally disable API checks if running in .NET Framework MSBuild. Task cannot run there. -->
     <EnableApiCheck Condition=" '$(MSBuildRuntimeType)' != 'Core' ">false</EnableApiCheck>