Flush stdout and stderr before shutdown in scripts

Although a test is present, it doesn't check the behavior because it seems that
in the test environment both streams are necessarily flushed

 #KT-9546 Fixed

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/KotlinToJVMBytecodeCompiler.kt

@@ -238,7 +238,14 @@ object KotlinToJVMBytecodeCompiler {
         val scriptConstructor = getScriptConstructor(scriptClass)
 
         try {
-            scriptConstructor.newInstance(*arrayOf<Any>(scriptArgs.toTypedArray()))
+            try {
+                scriptConstructor.newInstance(*arrayOf<Any>(scriptArgs.toTypedArray()))
+            }
+            finally {
+                // NB: these lines are required (see KT-9546) but aren't covered by tests
+                System.out.flush()
+                System.err.flush()
+            }
         }
         catch (e: Throwable) {
             reportExceptionFromScript(e)

compiler/testData/integration/smoke/scriptFlushBeforeShutdown/script.expected

@@ -0,0 +1,4 @@
+OUT:
+AB
+C
+Return code: 0

compiler/testData/integration/smoke/scriptFlushBeforeShutdown/script.kts

@@ -0,0 +1,3 @@
+print("A")
+println("B")
+print("C")

compiler/tests/org/jetbrains/kotlin/integration/CompilerSmokeTest.java

@@ -65,6 +65,10 @@ public class CompilerSmokeTest extends CompilerSmokeTestBase {
         runCompiler("script", "-script", "script.kts");
     }
 
+    public void testScriptFlushBeforeShutdown() throws Exception {
+        runCompiler("script", "-script", "script.kts");
+    }
+
     public void testCompileScript() throws Exception {
         String jar = tmpdir.getAbsolutePath() + File.separator + "script.jar";