Enable compatibility with non-hierarchical multiplatform projects

See: #71 (comment)
See: https://kotlinlang.org/docs/multiplatform-hierarchy.html#for-library-authors

Author: michaelbull

gradle.properties

@@ -3,6 +3,7 @@ version=1.1.16-SNAPSHOT
 
 kotlin.code.style=official
 kotlin.native.ignoreDisabledTargets=true
+kotlin.mpp.enableCompatibilityMetadataVariant=true
 kotlin.mpp.stability.nowarn=true
 
 org.gradle.jvmargs=-XX:MaxMetaspaceSize=1g