Always use x86 burn for bundle (#16150)

Author: PranavSenthilnathan

src/Microsoft.DotNet.Build.Tasks.Installers/build/wix5/wix.targets

@@ -23,7 +23,8 @@
     <PropertyGroup>
       <WixObjDir>$(IntermediateOutputPath)/wix/</WixObjDir>
       <WixObjDir Condition="'$(RuntimeIdentifier)' == ''">$(IntermediateOutputPath)/$(InstallerRuntimeIdentifier)/wix/</WixObjDir>
-      <MsiArch>$(InstallerTargetArchitecture)</MsiArch>
+      <MsiArch Condition="'$(GenerateExeBundle)' == 'true'">x86</MsiArch>
+      <MsiArch Condition="'$(GenerateExeBundle)' != 'true'">$(InstallerTargetArchitecture)</MsiArch>
     </PropertyGroup>
 
     <Error