[Test] Add ability to mute IC tests via fail.txt file

If fail.txt is present in root directory of test then exception from
  test will be muted. If there were no exceptions and fail.txt exists
  then test fail with suggestion to remove fail.txt

Content of fail.txt does not matter, so it can be used to store
  information about why this test doesn't pass

compiler/incremental-compilation-impl/test/org/jetbrains/kotlin/incremental/AbstractIncrementalCompilerRunnerTestBase.kt

@@ -42,7 +42,22 @@ abstract class AbstractIncrementalCompilerRunnerTestBase<Args : CommonCompilerAr
 
     fun doTest(path: String) {
         val testDir = File(path)
+        val failFile = testDir.resolve(FAIL_FILE_NAME)
+        var testPassed = false
+        try {
+            doTestImpl(testDir)
+            testPassed = true
+        } catch (e: Throwable) {
+            if (!failFile.exists()) {
+                throw e
+            }
+        }
+        if (testPassed && failFile.exists()) {
+            fail("Test is successful and $FAIL_FILE_NAME can be removed")
+        }
+    }
 
+    private fun doTestImpl(testDir: File) {
         fun Iterable<File>.relativePaths() =
             map { it.relativeTo(workingDir).path.replace('\\', '/') }
 
@@ -181,6 +196,7 @@ abstract class AbstractIncrementalCompilerRunnerTestBase<Args : CommonCompilerAr
         protected fun abiSnapshotFile(cacheDir: File): File = File(cacheDir, IncrementalCompilerRunner.ABI_SNAPSHOT_FILE_NAME)
 
         private const val ARGUMENTS_FILE_NAME = "args.txt"
+        private const val FAIL_FILE_NAME = "fail.txt"
 
         private fun parseAdditionalArgs(testDir: File): List<String> {
             return File(testDir, ARGUMENTS_FILE_NAME)