These binaries are built and copied from kotlin compiler: https://github.com/JetBrains/kotlin

Those prebuilt binaries are transient and therefore not signed. It's HIGHTLY RECOMMENDED to build the libraries by yourself and copy them here.

To build and copy the jars:

$ # setup kotlin build environment. see https://github.com/JetBrains/kotlin
$ cd path_to_kotlin_compiler_src
$ ./gradlew :compiler:tests-mutes:build :compiler:test-infrastructure-utils:testJar :compiler:tests-compiler-utils:testJar
$ cp compiler/tests-mutes/build/libs/*.jar .../repo
$ cp compiler/tests-compiler-utils/build/libs/tests-compiler-utils-<version>-tests.jar \
                                     .../repo/tests-compiler-utils-<version>.jar
$ cp compiler/test-infrastructure-utils/build/libs/test-infrastructure-utils-<version>tests.jar \
                                          .../repo/test-infrastructure-utils-<version>.jar