Try generating expression functions interface as function interface

[jbee]

The ExpressionFunctions interface originally was a Java functional interface with many default methods. After changing the source to kotlin MP the generated Java class is no longer a functional interface. This seems to require using compiler flags as described https://blog.jetbrains.com/kotlin/2020/07/kotlin-1-4-m3-generating-default-methods-in-interfaces/#jvmdefaultwithoutcompatibility

See also https://youtrack.jetbrains.com/issue/KT-63908