Reduce amount of redundant empty lines in C interop stubs

Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/StubGenerator.kt

@@ -1388,11 +1388,14 @@ class StubGenerator(
         out("")
 
         stubs.forEach {
-            it.nativeStubLines.forEach {
+            val lines = it.nativeStubLines
+            if (lines.isNotEmpty()) {
+                lines.forEach {
                     out(it)
                 }
                 out("")
             }
+        }
 
         if (entryPoint != null) {
             out("extern int Konan_main(int argc, char** argv);")