Use the version of urlencode/decode available on java 8

Author: ogolberg

buildSrc/src/main/kotlin/com/toasttab/protokt/gradle/ProtobufBuild.kt

@@ -25,7 +25,6 @@ import com.google.protobuf.gradle.protoc
 import com.google.protobuf.gradle.remove
 import java.io.File
 import java.net.URLEncoder
-import java.nio.charset.StandardCharsets
 import org.gradle.api.Project
 import org.gradle.api.file.FileCollection
 import org.gradle.api.plugins.JavaPluginConvention
@@ -86,7 +85,7 @@ private fun extraClasspath(project: Project, task: GenerateProtoTask): String {
         extensions += project.configurations.getByName(TEST_EXTENSIONS)
     }
 
-    return extensions.joinToString(";") { URLEncoder.encode(it.path, StandardCharsets.UTF_8) }
+    return extensions.joinToString(";") { URLEncoder.encode(it.path, "UTF-8") }
 }
 
 private fun configureSources(project: Project, generatedSourcesPath: String) {

protokt-codegen/src/main/kotlin/com/toasttab/protokt/codegen/protoc/ProtocolContext.kt

@@ -23,15 +23,14 @@ import com.toasttab.protokt.gradle.ONLY_GENERATE_GRPC
 import com.toasttab.protokt.gradle.RESPECT_JAVA_PACKAGE
 import com.toasttab.protokt.util.getProtoktVersion
 import java.net.URLDecoder
-import java.nio.charset.StandardCharsets
 
 class ProtocolContext(
     val fdp: FileDescriptorProto,
     val allPackagesByTypeName: Map<String, PPackage>,
     params: Map<String, String>
 ) {
     val classpath = params.getOrDefault(KOTLIN_EXTRA_CLASSPATH, "").split(";").map {
-        URLDecoder.decode(it, StandardCharsets.UTF_8)
+        URLDecoder.decode(it, "UTF-8")
     }
 
     val respectJavaPackage = respectJavaPackage(params)