Warn when --exclude///> using exclude does not actually exclude any files from the project

[Gedochao]

Version(s)
1.5.4 and 4ab3227

Describe the issue
When declaring a path or pattern in --exclude///> using exclude, I'd like a warning if no sources were actually caught by the pattern I declared. This would make it easier to catch when my exclusion actually works.
Additionally, I'd like some debug logs under -v -v -v telling me which files were, in fact, excluded.

[Gedochao]

Should start investigating at:

• scala-cli/modules/build/src/main/scala/scala/build/CrossSources.scala

  Lines 192 to 200 in bf3753e

  	val allExclude = { // supports only one exclude directive in one source file, which should be the project file.
  	val projectScalaFileOpt = flattenedInputs.collectFirst {
  	case f: ProjectScalaFile => f
  	}
  	val excludeFromProjectFile =
  	value(preprocessSources(projectScalaFileOpt.toSeq))
  	.flatMap(_.options).flatMap(_.internal.exclude)
  	exclude ++ excludeFromProjectFile
  	}