Add extra logging for `--cross`

[WojciechMazur]

Version(s)
1.4.0

Describe the bug
Based on scala/scala3#21194 the scala-cli does not detect multiple versions in the using scala directive.

To Reproduce
Compile following file

//> using scala 3.5.0-RC3, 3.nightly

def Test = ()

Expected behaviour
There should be a warning or error reported when parsing directives

[kavedaa]

Multiple versions are detected when run with e.g. scala-cli compile --power --cross test.scala.

(For the issue you are referring to, I only pasted the output from the first version, as the second was identical.)

Multiple versions are very useful when investigating which version(s) a particular bug/behaviour appears in, so I don't quite understand why it should be a warning/error.

[Gedochao]

As said in the comment above, the way it currently work is actually intentional.
We could, however, have a log message informing which version has been used for running/compilation (as Scala CLI will always use the first version passed in the directive)... and maybe another informing that multiple versions have been passed, but --cross was not enabled.