Tweak compiler check

Author: plemarquand

assets/test/targets/Plugins/BuildToolPlugin/BuildToolPlugin.swift

@@ -7,7 +7,7 @@ struct SimpleBuildToolPlugin: BuildToolPlugin {
         guard let sourceFiles = target.sourceModule?.sourceFiles else { return [] }
 
         // Build tool plugins are not being called on Windows with Swift < 6.0.
-        #if os(Windows) && swift(<6.0)
+        #if os(Windows) && !compiler(>=6.0)
         return []
         #endif