K2 kapt: add kapt.use.k2 Gradle property

... and `-Kapt-use-k2` CLI flag to enable K2 kapt.

 #KT-61114 Fixed

plugins/kapt3/kapt3-cli/src/KaptCli.kt

@@ -107,6 +107,7 @@ private fun transformKaptToolArgs(args: List<String>, messageCollector: MessageC
             }
             KaptCliOption.APT_MODE_OPTION -> aptModePassed = true
             KaptCliOption.VERBOSE_MODE_OPTION -> kaptVerboseModePassed = true
+            KaptCliOption.USE_K2 -> transformed.add("-Xuse-kapt4")
             else -> {}
         }
 

plugins/kapt3/kapt3-cli/src/KaptCliOption.kt

@@ -221,6 +221,13 @@ enum class KaptCliOption(
         cliToolOption = CliToolOption("-Kapt-use-jvm-ir", FLAG)
     ),
 
+    USE_K2(
+        "useK2",
+        "true | false",
+        "Use K2",
+        cliToolOption = CliToolOption("-Kapt-use-k2", FLAG)
+    ),
+
     DETECT_MEMORY_LEAKS_OPTION("detectMemoryLeaks", "true | false", "Detect memory leaks in annotation processors"),
     INCLUDE_COMPILE_CLASSPATH(
         "includeCompileClasspath",

plugins/kapt3/kapt3-cli/testData/integration-kapt4/kaptUseK2Flag/build.txt

@@ -0,0 +1,11 @@
+# kapt
+-language-version 2.0
+-Xsuppress-version-warnings
+-Kapt-use-k2=true
+-Kapt-mode=compile
+../simple/Test.kt
+
+# after
+Return code: 1
+
+error: [kapt] KAPT "compile" mode is not supported in Kotlin 2.x. Run kapt with -Kapt-mode=stubsAndApt and use kotlinc for the final compilation step.

plugins/kapt3/kapt3-cli/tests-gen/org/jetbrains/kotlin/kapt/cli/test/Kapt4ToolIntegrationTestGenerated.java

@@ -48,6 +48,12 @@ public class Kapt4ToolIntegrationTestGenerated extends AbstractKapt4ToolIntegrat
         runTest("plugins/kapt3/kapt3-cli/testData/integration-kapt4/defaultPackage/");
     }
 
+    @Test
+    @TestMetadata("kaptUseK2Flag")
+    public void testKaptUseK2Flag() throws Exception {
+        runTest("plugins/kapt3/kapt3-cli/testData/integration-kapt4/kaptUseK2Flag/");
+    }
+
     @Test
     @TestMetadata("kotlinFileGeneration")
     public void testKotlinFileGeneration() throws Exception {