K2JS: fix KT-5639 Exception in kotlin-js when directory is given instead of output file

#KT-5639 Fixed

compiler/tests/org/jetbrains/jet/cli/KotlincExecutableTestGenerated.java

@@ -174,6 +174,12 @@ public class KotlincExecutableTestGenerated extends AbstractKotlincExecutableTes
             doJsTest(fileName);
         }
 
+        @TestMetadata("outputIsDirectory.args")
+        public void testOutputIsDirectory() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/cli/js/outputIsDirectory.args");
+            doJsTest(fileName);
+        }
+
         @TestMetadata("outputPostfixFileNotFound.args")
         public void testOutputPostfixFileNotFound() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/cli/js/outputPostfixFileNotFound.args");

compiler/tests/org/jetbrains/jet/cli/js/K2JsCliTest.java

@@ -30,18 +30,25 @@ public class K2JsCliTest extends CliBaseTest {
         Assert.assertTrue(new File(tmpdir.getTmpDir(), "out.js").isFile());
     }
 
+    @Test
+    public void outputIsDirectory() throws Exception {
+        executeCompilerCompareOutputJS();
+
+        Assert.assertFalse(new File(tmpdir.getTmpDir(), "out.js").exists());
+    }
+
     @Test
     public void outputPrefixFileNotFound() throws Exception {
         executeCompilerCompareOutputJS();
 
-        Assert.assertFalse(new File(tmpdir.getTmpDir(), "out.js").isFile());
+        Assert.assertFalse(new File(tmpdir.getTmpDir(), "out.js").exists());
     }
 
     @Test
     public void outputPostfixFileNotFound() throws Exception {
         executeCompilerCompareOutputJS();
 
-        Assert.assertFalse(new File(tmpdir.getTmpDir(), "out.js").isFile());
+        Assert.assertFalse(new File(tmpdir.getTmpDir(), "out.js").exists());
     }
 
     @Test