[K/N][test] Replace genKt39548 task with doBeforeBuild closure

kotlin-native/backend.native/tests/build.gradle

@@ -3727,12 +3727,6 @@ task deserialized_fields(type: KonanLocalTest) {
     source = "serialization/deserialized_fields.kt"
 }
 
-task genKt39548 {
-    doFirst {
-        GenTestKT39548Kt.genTestKT39548(file("$buildDir/kt39548/kt39548.kt"))
-    }
-}
-
 KotlinNativeTestKt.createTest(project, "kt39548", KonanStandaloneTest) { task ->
     // Test infrastructure doesn't support generated source;
     // workaround by specifying dummy source:
@@ -3743,13 +3737,14 @@ KotlinNativeTestKt.createTest(project, "kt39548", KonanStandaloneTest) { task ->
         konanArtifacts {
             program(name, targets: [target.name]) {
                 baseDir   "$testOutputLocal/$name"
-                srcFiles  "$buildDir/kt39548/kt39548.kt" // Generated by genKt39548 task.
+                srcFiles  "$buildDir/kt39548/kt39548.kt" // Generated by doBeforeBuild task.
                 extraOpts task.flags
                 extraOpts project.globalTestArgs
             }
         }
-
-        UtilsKt.findKonanBuildTask(project, name, target).dependsOn(genKt39548)
+        doBeforeBuild {
+            GenTestKT39548Kt.genTestKT39548(file("$buildDir/kt39548/kt39548.kt"))
+        }
     }
 }