Add runtime string concat options. Some renaming

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JVMCompilerArguments.kt

@@ -334,6 +334,16 @@ class K2JVMCompilerArguments : CommonCompilerArguments() {
     )
     var emitJvmTypeAnnotations: Boolean by FreezableVar(false)
 
+    @Argument(
+        value = "-Xruntime-string-concat",
+        valueDescription = "{disable|enable|indy}",
+        description = """Switch a way in which string concatenation is performed.
+-Xruntime-string-concat=enable          Performs string concatenation via `invokedynamic` 'makeConcatWithConstants'. Works only with `-jvm-target 9` or greater  
+-Xruntime-string-concat=indy            Performs string concatenation via `invokedynamic` 'makeConcat'. Works only with `-jvm-target 9` or greater                                 
+-Xruntime-string-concat=disable         Performs string concatenation via `StringBuilder`"""
+    )
+    var runtimeStringConcat: String? by NullableStringFreezableVar(JvmRuntimeStringConcat.DISABLE.name.toLowerCase())
+
     @Argument(
         value = "-Xklib",
         valueDescription = "<path>",

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

@@ -49,6 +49,24 @@ fun CompilerConfiguration.setupJvmSpecificArguments(arguments: K2JVMCompilerArgu
         }
     }
 
+    if (arguments.runtimeStringConcat != null) {
+        val runtimeStringConcat = JvmRuntimeStringConcat.fromString(arguments.runtimeStringConcat!!)
+        if (runtimeStringConcat != null) {
+            put(JVMConfigurationKeys.RUNTIME_STRING_CONCAT, runtimeStringConcat)
+            if (jvmTarget.bytecodeVersion < JvmTarget.JVM_9.bytecodeVersion && runtimeStringConcat != JvmRuntimeStringConcat.DISABLE) {
+                messageCollector.report(
+                    WARNING,
+                    "`-Xruntime-string-concat=${arguments.runtimeStringConcat}` does nothing with JVM target `${jvmTarget.description}`."
+                )
+            }
+        } else {
+            messageCollector.report(
+                ERROR, "Unknown `runtime-string-concat` mode: ${arguments.jvmTarget}\n" +
+                        "Supported versions: ${JvmRuntimeStringConcat.values().joinToString { it.name.toLowerCase() }}"
+            )
+        }
+    }
+
     addAll(JVMConfigurationKeys.ADDITIONAL_JAVA_MODULES, arguments.additionalJavaModules?.asList())
 }