Do not call IR backend when there's a script involved

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

@@ -39,8 +39,7 @@ import org.jetbrains.kotlin.cli.common.ExitCode
 import org.jetbrains.kotlin.cli.common.checkKotlinPackageUsage
 import org.jetbrains.kotlin.cli.common.config.addKotlinSourceRoot
 import org.jetbrains.kotlin.cli.common.messages.AnalyzerWithCompilerReport
-import org.jetbrains.kotlin.cli.common.messages.CompilerMessageSeverity.OUTPUT
+import org.jetbrains.kotlin.cli.common.messages.CompilerMessageSeverity.*
-import org.jetbrains.kotlin.cli.common.messages.CompilerMessageSeverity.WARNING
 import org.jetbrains.kotlin.cli.common.messages.MessageCollector
 import org.jetbrains.kotlin.cli.common.messages.OutputMessageUtil
 import org.jetbrains.kotlin.cli.common.output.writeAll
@@ -612,8 +611,17 @@ object KotlinToJVMBytecodeCompiler {
         sourceFiles: List<KtFile>,
         module: Module?
     ): GenerationState {
-        val isIR = configuration.getBoolean(JVMConfigurationKeys.IR) ||
+        // The IR backend does not handle .kts files yet.
-                configuration.getBoolean(CommonConfigurationKeys.USE_FIR)
+        var isIR = (configuration.getBoolean(JVMConfigurationKeys.IR) ||
+                configuration.getBoolean(CommonConfigurationKeys.USE_FIR))
+        val anyKts = sourceFiles.any { it.isScript() }
+        if (isIR && anyKts) {
+            environment.messageCollector.report(
+                STRONG_WARNING,
+                "IR backend does not support .kts scripts, switching to old JVM backend"
+            )
+            isIR = false
+        }
         val generationState = GenerationState.Builder(
             environment.project,
             ClassBuilderFactories.BINARIES,