Do not add current directory to "kotlin" classpath

As "java" does, do not include the current directory to the classpath if
the explicit classpath is specified. This is more stable than always
adding the current directory, and users can easily add the ".:" to the
beginning of the explicit classpath themselves

 #KT-17100 Fixed

compiler/cli/cli-runner/src/org/jetbrains/kotlin/runner/Main.kt

@@ -40,8 +40,6 @@ object Main {
         val arguments = arrayListOf<String>()
         var noReflect = false
 
-        classpath.addPaths(".")
-
         var i = 0
         while (i < args.size) {
             val arg = args[i]
@@ -65,7 +63,9 @@ object Main {
                 printVersionAndExit()
             }
             else if ("-classpath" == arg || "-cp" == arg) {
-                classpath.addPaths(next())
+                for (path in next().split(File.pathSeparator).filter(String::isNotEmpty)) {
+                    classpath.addPath(path)
+                }
             }
             else if ("-expression" == arg || "-e" == arg) {
                 runner = ExpressionRunner(next())
@@ -92,10 +92,14 @@ object Main {
             i++
         }
 
-        classpath.addPaths(KOTLIN_HOME.toString() + "/lib/kotlin-runtime.jar")
+        if (classpath.isEmpty()) {
+            classpath.addPath(".")
+        }
+
+        classpath.addPath(KOTLIN_HOME.toString() + "/lib/kotlin-runtime.jar")
 
         if (!noReflect) {
-            classpath.addPaths(KOTLIN_HOME.toString() + "/lib/kotlin-reflect.jar")
+            classpath.addPath(KOTLIN_HOME.toString() + "/lib/kotlin-reflect.jar")
         }
 
         if (runner == null) {
@@ -105,10 +109,8 @@ object Main {
         runner.run(classpath, arguments)
     }
 
-    private fun MutableList<URL>.addPaths(paths: String) {
-        for (path in paths.split(File.pathSeparator)) {
-            add(File(path).absoluteFile.toURI().toURL())
-        }
+    private fun MutableList<URL>.addPath(path: String) {
+        add(File(path).absoluteFile.toURI().toURL())
     }
 
     @JvmStatic