Prohibit JVM target 1.6

But still compile stdlib, reflect, kotlin.test and scripting runtimes
with JVM target 1.6 to simplify migration from Kotlin 1.6 to 1.7.

 #KT-45165 Fixed

compiler/testData/cli/jvm/extraHelp.out

@@ -131,7 +131,8 @@ where advanced options include:
                              Specify behavior for Checker Framework compatqual annotations (NullableDecl/NonNullDecl).
                              Default value is 'enable'
   -Xsuppress-deprecated-jvm-target-warning
-                             Suppress deprecation warning about deprecated JVM target versions
+                             Suppress deprecation warning about deprecated JVM target versions.
+                             This option has no effect and will be deleted in a future version.
   -Xsuppress-missing-builtins-error
                              Suppress the "cannot access built-in declaration" error (useful with -no-stdlib)
   -Xtype-enhancement-improvements-strict-mode

compiler/testData/cli/jvm/help.out

@@ -6,7 +6,7 @@ where possible options include:
   -include-runtime           Include Kotlin runtime into the resulting JAR
   -java-parameters           Generate metadata for Java 1.8 reflection on method parameters
   -jdk-home <path>           Include a custom JDK from the specified location into the classpath instead of the default JAVA_HOME
-  -jvm-target <version>      Target version of the generated JVM bytecode (1.6 (DEPRECATED), 1.8, 9, 10, ..., 18), default is 1.8
+  -jvm-target <version>      Target version of the generated JVM bytecode (1.8, 9, 10, ..., 18), default is 1.8
   -module-name <name>        Name of the generated .kotlin_module file
   -no-jdk                    Don't automatically include the Java runtime into the classpath
   -no-reflect                Don't automatically include Kotlin reflection into the classpath

compiler/testData/cli/jvm/jvm6Target.out

@@ -1,2 +1,2 @@
-warning: JVM target 1.6 is deprecated and will be removed in a future release. Please migrate to JVM target 1.8 or above
-OK
+error: JVM target 1.6 is no longer supported. Please migrate to JVM target 1.8 or above
+COMPILATION_ERROR

compiler/testData/cli/jvm/jvmDefaultAll.out

@@ -1,3 +1,3 @@
-warning: JVM target 1.6 is deprecated and will be removed in a future release. Please migrate to JVM target 1.8 or above
+error: JVM target 1.6 is no longer supported. Please migrate to JVM target 1.8 or above
 error: '-Xjvm-default=all' is only supported since JVM target 1.8. Recompile with '-jvm-target 1.8'
 COMPILATION_ERROR