Use MD5 when caching class ABI structure

This avoids Kotlin Gradle plugin dependency
on Guava, and it is a good hash function for this
use-case.

Also fix some formatting.

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/incremental/ClassAbiExtractor.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.gradle.internal.kapt.incremental
 import org.jetbrains.org.objectweb.asm.*
 
 const val metadataDescriptor: String = "Lkotlin/Metadata;"
+
 class ClassAbiExtractor(private val writer: ClassWriter) : ClassVisitor(Opcodes.API_VERSION, writer) {
 
     override fun visitMethod(

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/incremental/ClassTypeExtractorVisitor.kt

@@ -17,7 +17,7 @@ class ClassTypeExtractorVisitor(visitor: ClassVisitor) : ClassVisitor(Opcodes.AP
     private lateinit var classInternalName: String
 
     fun getAbiTypes() = abiTypes.filter { !toIgnore.contains(it) && it != classInternalName }.toSet()
-    fun getPrivateTypes() = privateTypes.filter { !toIgnore.contains(it) && it != classInternalName && !abiTypes.contains(it)}.toSet()
+    fun getPrivateTypes() = privateTypes.filter { !toIgnore.contains(it) && it != classInternalName && !abiTypes.contains(it) }.toSet()
 
     override fun visit(version: Int, access: Int, name: String?, signature: String?, superName: String?, interfaces: Array<out String>?) {
         super.visit(version, access, name, signature, superName, interfaces)

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/incremental/ClasspathAnalyzer.kt

@@ -5,11 +5,11 @@
 
 package org.jetbrains.kotlin.gradle.internal.kapt.incremental
 
-import com.google.common.hash.Hashing
 import org.gradle.api.artifacts.transform.ArtifactTransform
 import org.jetbrains.org.objectweb.asm.ClassReader
 import org.jetbrains.org.objectweb.asm.ClassWriter
 import java.io.*
+import java.security.MessageDigest
 import java.util.zip.ZipFile
 
 const val CLASS_STRUCTURE_ARTIFACT_TYPE = "class-structure"
@@ -75,8 +75,9 @@ private fun analyzeInputStream(input: InputStream, internalName: String, entryDa
     )
 
     val bytes = abiExtractor.getBytes()
-    val hashBytes = Hashing.murmur3_128().hashBytes(bytes)
-    entryData.classAbiHash[internalName] = hashBytes.asBytes()
+    val digest = MessageDigest.getInstance("MD5").digest(bytes)
+
+    entryData.classAbiHash[internalName] = digest
     entryData.classDependencies[internalName] =
         ClassDependencies(typeDependenciesExtractor.getAbiTypes(), typeDependenciesExtractor.getPrivateTypes())
 }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/internal/kapt/incremental/ClasspathSnapshot.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.gradle.internal.kapt.incremental
 
 import java.io.*
 import java.util.*
+
 open class ClasspathSnapshot protected constructor(
     private val cacheDir: File,
     private val classpath: Iterable<File>,
@@ -146,7 +147,7 @@ open class ClasspathSnapshot protected constructor(
 
         val allImpacted = mutableSetOf<String>()
         var current = changedClasses
-        while(current.isNotEmpty()) {
+        while (current.isNotEmpty()) {
             val newRound = mutableSetOf<String>()
             for (klass in current) {
                 if (allImpacted.add(klass)) {