Support -Xjdk-release=8 as alias for -Xjdk-release=1.8

#KT-53278 Fixed

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

@@ -51,7 +51,12 @@ fun CompilerConfiguration.setupJvmSpecificArguments(arguments: K2JVMCompilerArgu
         }
     }
 
-    val jvmTargetValue = releaseTargetArg ?: jvmTargetArg
+    val jvmTargetValue = when (releaseTargetArg) {
+        "6" -> "1.6"
+        "8" -> "1.8"
+        null -> jvmTargetArg
+        else -> releaseTargetArg
+    }
     if (jvmTargetValue != null) {
         val jvmTarget = JvmTarget.fromString(jvmTargetValue)
         if (jvmTarget != null) {

compiler/testData/cli/jvm/jdkRelease8.args

@@ -0,0 +1,4 @@
+-Xjdk-release=8
+$TESTDATA_DIR$/jdkRelease.kt
+-d
+$TEMP_DIR$

compiler/testData/cli/jvm/jdkRelease8.out

@@ -0,0 +1 @@
+OK

compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java

@@ -607,6 +607,11 @@ public class CliTestGenerated extends AbstractCliTest {
             runTest("compiler/testData/cli/jvm/jdkRelease.args");
         }
 
+        @TestMetadata("jdkRelease8.args")
+        public void testJdkRelease8() throws Exception {
+            runTest("compiler/testData/cli/jvm/jdkRelease8.args");
+        }
+
         @TestMetadata("jspecifyByLv15.args")
         public void testJspecifyByLv15() throws Exception {
             runTest("compiler/testData/cli/jvm/jspecifyByLv15.args");