chore: skip Setup/SetupBootstrapper build when WiX is not installed

Agent-Logs-Url: https://github.com/spaghettidba/WorkloadTools/sessions/9e17984c-014d-4765-a5f1-b320fe77795b

Co-authored-by: spaghettidba <7592822+spaghettidba@users.noreply.github.com>

Author: Copilot

Setup/Setup.wixproj

@@ -58,8 +58,11 @@
   <PropertyGroup>
     <PostBuildEvent>call $(ProjectDir)postbuild.bat "$(TargetPath)" "$(TargetDir)WorkloadTools_$(Platform)$(TargetExt)"</PostBuildEvent>
   </PropertyGroup>
-  <Import Project="$(WixTargetsPath)" />
+  <Import Project="$(WixTargetsPath)" Condition="Exists('$(WixTargetsPath)')" />
   <Target Name="EnsureWixTargetsImported" BeforeTargets="PrepareForBuild" Condition=" '$(WixTargetsImported)' == '' ">
-    <Error Text="WiX Toolset v3 build targets were not found at '$(WixTargetsPath)'. Please install WiX Toolset v3.x from https://wixtoolset.org/." />
+    <Warning Text="WiX Toolset v3 build targets were not found at '$(WixTargetsPath)'. Build skipped. Use buildmsi.ps1 to build the installer." />
+  </Target>
+  <Target Name="Build" Condition=" '$(WixTargetsImported)' == '' ">
+    <Message Text="Setup project skipped: WiX Toolset v3 is not installed. Use buildmsi.ps1 to build the installer." Importance="high" />
   </Target>
 </Project>

SetupBootstrapper/SetupBootstrapper.wixproj

@@ -61,8 +61,11 @@
   <PropertyGroup>
     <PostBuildEvent>call $(ProjectDir)postbuild.bat "$(TargetPath)" "$(TargetDir)WorkloadTools_$(Platform)$(TargetExt)"</PostBuildEvent>
   </PropertyGroup>
-  <Import Project="$(WixTargetsPath)" />
+  <Import Project="$(WixTargetsPath)" Condition="Exists('$(WixTargetsPath)')" />
   <Target Name="EnsureWixTargetsImported" BeforeTargets="PrepareForBuild" Condition=" '$(WixTargetsImported)' == '' ">
-    <Error Text="WiX Toolset v3 build targets were not found at '$(WixTargetsPath)'. Please install WiX Toolset v3.x from https://wixtoolset.org/." />
+    <Warning Text="WiX Toolset v3 build targets were not found at '$(WixTargetsPath)'. Build skipped. Use buildexe.ps1 to build the bootstrapper." />
+  </Target>
+  <Target Name="Build" Condition=" '$(WixTargetsImported)' == '' ">
+    <Message Text="SetupBootstrapper project skipped: WiX Toolset v3 is not installed. Use buildexe.ps1 to build the bootstrapper." Importance="high" />
   </Target>
 </Project>