Do not produce libraries json declarations dump

It's no longer needed for checking binary compatibility.
Clean build of these libraries is no longer required too.

Cleanup build.gradle of binary-compatibility-validator.

libraries/stdlib/runtime/build.gradle

@@ -43,7 +43,6 @@ compileKotlin {
         freeCompilerArgs = [
                 "-Xallow-kotlin-package",
                 "-Xnormalize-constructor-calls=enable",
-                "-Xdump-declarations-to=${buildDir}/runtime-declarations.json",
                 "-Xmulti-platform",
                 "-cp", "${rootDir}/dist/builtins",
                 "-module-name", project.name