Migrate binary-compatibility-validator tests to gradle.

Author: ilya-g

src/test/kotlin/org.jetbrains.kotlin.tools.tests/CasesPublicAPITest.kt

@@ -8,8 +8,8 @@ import java.io.File
 class CasesPublicAPITest {
 
  companion object {
- val visibilities = readKotlinVisibilities(File("target/cases-declarations.json"))
- val baseClassPath = File("target/test-classes/cases").absoluteFile
+ val visibilities = readKotlinVisibilities(File("build/cases-declarations.json"))
+ val baseClassPath = File("build/classes/test/cases").absoluteFile
  val baseOutputPath = File("src/test/kotlin/cases")
  }