This makes Kotlin resolve possible to resolve from libraries (kotlinc libraries in our case)
to sources (IJ platfrom sources in our case). See - KT-24309

This commit fixes unresolved references (of classes from kotlinc) in IDE

Q: Why do we need `community/plugins/kotlin/kotlin-compiler-classpath/src/.gitkeep`?
A: Because if anchor module doesn't have source root then kotlin resolve ignores this module

GitOrigin-RevId: d01be9c4e511c399a0e5f33bbea85709ebb44a28