Fixing the condition under which PlatformTarget is set

scripts/build.ps1

@@ -145,8 +145,7 @@ try {
       $architecture = "<auto>"
     }
   }
-
-  if (($architecture -ne "") -and ($architecture -ne "<auto>")) {
+  elseif (($architecture -ne "") -and ($architecture -ne "<auto>")) {
     $properties += "/p:PlatformTarget=$architecture"
   }