JS: tests for KT-7357: extension functions from external KJS library couldn't be called in some cases

compiler/testData/integration/ant/js/simpleWithStdlibAndJsFileAsAnotherLib/root1/foo.kt

@@ -0,0 +1,17 @@
+package foo
+
+import library.sample.*
+import kotlin.js.Date
+
+var ok = "FAIL"
+
+fun main(args: Array<String>) {
+    val x = ClassA().value
+    if (x == 100) {
+        ok = "OK"
+    }
+    val date = Date()
+    println(date.extFun())
+}
+
+fun box(): String = ok