Prevent scala-{library,reflect} from depending on JVM code outside of compact1 profile

[adriaanm]

In 2.13.0-M3, we will have shed all dependencies outside of the compact1 profile. Let's make sure to keep it that way.

[adriaanm]

Can we use jdeps somehow?

[adriaanm]

@dwijnand could you take a stab at integrating my proposed test over at scala/scala#6164 (comment) into the build?