Fix JavaExec.main deprecation

compiler/fir/checkers/build.gradle.kts

@@ -52,7 +52,7 @@ val generateCheckersComponents by tasks.registering(NoDebugJavaExec::class) {
     args(generationRoot, *platformGenerationRoots.toTypedArray())
     workingDir = rootDir
     classpath = generatorClasspath
-    main = "org.jetbrains.kotlin.fir.checkers.generator.MainKt"
+    mainClass.set("org.jetbrains.kotlin.fir.checkers.generator.MainKt")
     systemProperties["line.separator"] = "\n"
 }
 

compiler/fir/tree/build.gradle.kts

@@ -42,7 +42,7 @@ val generateTree by tasks.registering(NoDebugJavaExec::class) {
     args(generationRoot)
     workingDir = rootDir
     classpath = generatorClasspath
-    main = "org.jetbrains.kotlin.fir.tree.generator.MainKt"
+    mainClass.set("org.jetbrains.kotlin.fir.tree.generator.MainKt")
     systemProperties["line.separator"] = "\n"
 }
 

core/builtins/build.gradle.kts

@@ -61,7 +61,7 @@ fun serializeTask(name: String, sourcesTask: TaskProvider<*>, inDirs: List<File>
         outputs.cacheIf { true }
 
         classpath(rootProject.buildscript.configurations["bootstrapCompilerClasspath"])
-        main = "org.jetbrains.kotlin.serialization.builtins.RunKt"
+        mainClass.set("org.jetbrains.kotlin.serialization.builtins.RunKt")
         jvmArgs(listOfNotNull(
             "-Didea.io.use.nio2=true",
             "-Dkotlin.builtins.serializer.log=true".takeIf { logger.isInfoEnabled }

libraries/stdlib/js-v1/build.gradle

@@ -172,7 +172,7 @@ task compileJs(type: NoDebugJavaExec) {
         include '**/*.js'
     }
 
-    main = "org.jetbrains.kotlin.cli.js.internal.JSStdlibLinker"
+    mainClass = "org.jetbrains.kotlin.cli.js.internal.JSStdlibLinker"
 
     // local variables for configuration cache work
     def rootDir = rootDir

libraries/tools/kotlin-stdlib-gen/build.gradle

@@ -30,7 +30,7 @@ processResources {
 
 task run(type: JavaExec) {
     group 'application'
-    main 'generators.GenerateStandardLibKt'
+    mainClass = 'generators.GenerateStandardLibKt'
     classpath sourceSets.main.runtimeClasspath
     args = ["${rootDir}"]
     systemProperty 'line.separator', '\n'
@@ -38,7 +38,7 @@ task run(type: JavaExec) {
 
 task generateStdlibTests(type: JavaExec) {
     group 'application'
-    main 'generators.GenerateStandardLibTestsKt'
+    mainClass = 'generators.GenerateStandardLibTestsKt'
     classpath sourceSets.main.runtimeClasspath
     args = ["${rootDir}"]
     systemProperty 'line.separator', '\n'
@@ -46,7 +46,7 @@ task generateStdlibTests(type: JavaExec) {
 
 task generateUnicodeData(type: JavaExec) {
     group 'application'
-    main 'generators.unicode.GenerateUnicodeDataKt'
+    mainClass = 'generators.unicode.GenerateUnicodeDataKt'
     classpath sourceSets.main.runtimeClasspath
     args = ["${rootDir}"]
-}
+}