add warning if target has `**/*`

As part of writing up a post on [expected Gradle configuration performance](https://www.liutikas.net/2025/11/02/Unreasonable-Configuration.html) I found that com.diffplug.spotless causes 17 second regression in configuration performance [Androidify](https://github.com/android/androidify) Gradle project.

Simply removing com.diffplug.spotless from root build.gradle.kts and rerunning the Gradle profiler we get configuration time from 26s to 9s.