Default to ILC host architecture that matches OS architecture on Wind…

…ows (#80752)

It allows compilation using msbuild.exe that is x86 by default

src/coreclr/nativeaot/BuildIntegration/Microsoft.DotNet.ILCompiler.SingleEntry.targets

@@ -17,10 +17,12 @@
 
     <RuntimeIlcPackageName>runtime.$(OSIdentifier)-$(TargetArchitecture).Microsoft.DotNet.ILCompiler</RuntimeIlcPackageName>
 
-    <!-- Default to host that matches SDK architecture -->
+    <!-- Default to host that matches OS architecture on Windows. It allows compilation using msbuild.exe that is x86 by default -->
+    <IlcHostArch Condition="'$(OS)' == 'Windows_NT' and '$(IlcHostArch)' == ''">$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture.ToString().ToLowerInvariant)</IlcHostArch>
+    <!-- Default to host that matches SDK architecture on non-Windows -->
     <IlcHostArch Condition="'$(IlcHostArch)' == ''">$([System.Runtime.InteropServices.RuntimeInformation]::ProcessArchitecture.ToString().ToLowerInvariant)</IlcHostArch>
     <IlcHostPackageName>runtime.$(OSIdentifier)-$(IlcHostArch).Microsoft.DotNet.ILCompiler</IlcHostPackageName>
-    
+
     <IlcCalledViaPackage>true</IlcCalledViaPackage>
   </PropertyGroup>
 

src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.Unix.targets

@@ -29,7 +29,7 @@ The .NET Foundation licenses this file to you under the MIT license.
       <FullRuntimeName Condition="'$(ServerGarbageCollection)' == 'true'">libRuntime.ServerGC</FullRuntimeName>
 
       <CrossCompileRid />
-      <CrossCompileRid Condition="!$(RuntimeIdentifier.EndsWith('-$(OSHostArch)'))">$(RuntimeIdentifier)</CrossCompileRid>
+      <CrossCompileRid Condition="!$(RuntimeIdentifier.EndsWith('-$(IlcHostArch)'))">$(RuntimeIdentifier)</CrossCompileRid>
 
       <CrossCompileArch />
       <CrossCompileArch Condition="$(CrossCompileRid.EndsWith('-x64'))">x86_64</CrossCompileArch>