bpo-46948: Fix launcher installer build failure due to first part of fix (GH-31920) (GH-31925)

(cherry picked from commit 70881208)

Co-authored-by: Steve Dower <steve.dower@python.org>

Tools/msi/common.wxs

@@ -61,6 +61,7 @@
     </Fragment>
 
     <Fragment>
+        <?ifdef PythonExeComponentGuid ?>
         <!-- Locate TARGETDIR automatically assuming we have executables installed -->
         <Property Id="TARGETDIR">
             <ComponentSearch Id="PythonExe_Directory" Guid="$(var.PythonExeComponentGuid)">
@@ -69,6 +70,7 @@
                 </DirectorySearch>
             </ComponentSearch>
         </Property>
+        <?endif ?>
         <Property Id="DetectTargetDir" Value="1" />
     </Fragment>