Exclude duplicate classes for Jar task

This change changes the `duplicatesStrategy` for the `jmhBenchmarkJar` tasks to exclude duplicate classes.
With Gradle 7, complex dependencies (where the same class might exist multiple times) can cause the build to 
fail due to the default `duplicatesStrategy` triggering a failure.

Fixes #39

Author: fabianishere

plugin/main/src/kotlinx/benchmark/gradle/JvmTasks.kt

@@ -31,7 +31,9 @@ fun Project.createJvmBenchmarkCompileTask(target: JvmBenchmarkTarget, compileCla
         dependsOn("${target.name}${BenchmarksPlugin.BENCHMARK_COMPILE_SUFFIX}")
         conventionMapping.map("classifier") { "JMH" }
         manifest.attributes["Main-Class"] = "org.openjdk.jmh.Main"
-
+        
+        duplicatesStrategy = DuplicatesStrategy.EXCLUDE
+        
         from(project.provider {
             compileClasspath.map {
                 when {