Declare generated SourceSets correctly

Allow Gradle to keep the track of the task generating the sources
KTI-1502 Fixed

libraries/tools/kotlin-stdlib-gen/build.gradle.kts

@@ -4,18 +4,17 @@ plugins {
 
 val copyrightDirectory = project.layout.buildDirectory.dir("copyright")
 
-sourceSets {
-    "main" {
-        kotlin.srcDir("src")
-        resources.srcDir(copyrightDirectory)
-    }
-}
-
 dependencies {
     api("org.jetbrains.kotlin:kotlin-stdlib:$bootstrapKotlinVersion")
     api("org.jetbrains.kotlin:kotlin-reflect:$bootstrapKotlinVersion")
 }
 
+val copyCopyrightProfile by tasks.registering(Copy::class) {
+    from("$rootDir/.idea/copyright")
+    into(copyrightDirectory)
+    include("apache.xml")
+}
+
 tasks {
     compileKotlin {
         compilerOptions {
@@ -23,16 +22,6 @@ tasks {
         }
     }
 
-    val copyCopyrightProfile by registering(Copy::class) {
-        from("$rootDir/.idea/copyright")
-        into(copyrightDirectory)
-        include("apache.xml")
-    }
-
-    processResources {
-        dependsOn(copyCopyrightProfile)
-    }
-
     register<JavaExec>("run") {
         group = "application"
         mainClass = "generators.GenerateStandardLibKt"
@@ -55,4 +44,11 @@ tasks {
         classpath = sourceSets.main.get().runtimeClasspath
         args = listOf("$rootDir")
     }
-}
+}
+
+sourceSets {
+    "main" {
+        kotlin.srcDir("src")
+        resources.srcDir(copyCopyrightProfile)
+    }
+}