Handle whitespaces in argfiles correctly

#KT-27218 Fixed

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/preprocessCommandLineArguments.kt

@@ -16,8 +16,6 @@ private const val EXPERIMENTAL_ARGFILE_ARGUMENT = "-Xargfile="
 private const val SINGLE_QUOTE = '\''
 private const val DOUBLE_QUOTE = '"'
 private const val BACKSLASH = '\\'
-private const val WHITESPACE = ' '
-private const val NEWLINE = '\n'
 
 /**
  * Performs initial preprocessing of arguments, passed to the compiler.
@@ -56,13 +54,14 @@ private fun Reader.parseNextArgument(): String? {
     val sb = StringBuilder()
 
     var r = nextChar()
-    while (r != null && (r == WHITESPACE || r == NEWLINE)) {
+    while (r != null && r.isWhitespace()) {
         r = nextChar()
     }
 
-    loop@ while (r != null) {
+    while (r != null) {
+        if (r.isWhitespace()) break
+
         when (r) {
-            WHITESPACE, NEWLINE -> break@loop
             DOUBLE_QUOTE, SINGLE_QUOTE -> consumeRestOfEscapedSequence(sb, r)
             BACKSLASH -> nextChar()?.apply(sb::append)
             else -> sb.append(r)

compiler/tests/org/jetbrains/kotlin/cli/CustomCliTest.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.cli
+
+import org.jetbrains.kotlin.cli.jvm.K2JVMCompiler
+import org.jetbrains.kotlin.test.CompilerTestUtil
+import org.jetbrains.kotlin.test.TestCaseWithTmpdir
+import java.io.File
+
+class CustomCliTest : TestCaseWithTmpdir() {
+    fun testArgfileWithNonTrivialWhitespaces() {
+        val text = "-include-runtime\r\n\t\t-language-version\n\t1.2\r\n-version"
+        val argfile = File(tmpdir, "argfile").apply { writeText(text, Charsets.UTF_8) }
+        CompilerTestUtil.executeCompilerAssertSuccessful(K2JVMCompiler(), listOf("@" + argfile.absolutePath))
+    }
+}