Appears that plugin classpath can contain not only `File.separatorChar`, but also '/' on Windows. Without the proper handling of this case, Gradle importer may import the plugin JAR made for Gradle with shaded 'com.intellij' and cause an exception during the JPS build.
Use the bundled compiler plugins for Maven projects (as we do for Gradle projects already) because the plugin provided as a dependency in the POM file may have an incompatible version.