Set minimal supported Gradle version to 6.8.3

^KT-53885 Fixed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/ConfigurationCacheForAndroidIT.kt

@@ -11,7 +11,6 @@ import org.jetbrains.kotlin.gradle.testbase.TestVersions.AGP.AGP_42
 import org.junit.jupiter.api.DisplayName
 
 @DisplayName("Configuration cache in Android project")
-@GradleTestVersions(minVersion = TestVersions.Gradle.G_6_7)
 @JvmGradlePluginTests
 class ConfigurationCacheForAndroidIT : AbstractConfigurationCacheIT() {
     override val defaultBuildOptions = super.defaultBuildOptions.copy(

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/testbase/TestVersions.kt

@@ -11,7 +11,6 @@ import org.jetbrains.kotlin.gradle.utils.minSupportedGradleVersion
 
 interface TestVersions {
     object Gradle {
-        const val G_6_7 = "6.7.1"
         const val G_6_8 = "6.8.3"
         const val G_6_9 = "6.9.2"
         const val G_7_0 = "7.0.2"

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/testbase/argumentProviders.kt

@@ -136,7 +136,7 @@ class GradleAndJdkArgumentsProvider : GradleArgumentsProvider() {
 
     companion object {
         private val jdkGradleCompatibilityMatrix = mapOf(
-            JavaVersion.VERSION_15 to GradleVersion.version(TestVersions.Gradle.G_6_7),
+            JavaVersion.VERSION_15 to GradleVersion.version(TestVersions.Gradle.G_6_8),
             JavaVersion.VERSION_16 to GradleVersion.version(TestVersions.Gradle.G_7_0),
             JavaVersion.VERSION_17 to GradleVersion.version(TestVersions.Gradle.G_7_3)
         )

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/tasks/configuration/KaptGenerateStubsConfig.kt

@@ -138,9 +138,8 @@ internal class KaptGenerateStubsConfig : BaseKotlinCompileConfig<KaptGenerateStu
     }
 
     private val shouldUseFileTreeKaptFilter
-        get() = isGradleVersionAtLeast(7, 5) || !isConfigurationCacheAvailable(project.gradle) && isGradleVersionAtLeast(6, 8)
+        get() = isGradleVersionAtLeast(7, 5) || !isConfigurationCacheAvailable(project.gradle)
 
-    // Filtering through FileTree and PatternFilterable works faster, but adds empty directories which is the problem for Gradle 6.7
     private class FileTreeKaptInputsFilter(val spec: KaptFilterSpec) : CachingKaptInputsFilter() {
         override fun filtered(fileCollection: FileCollection): FileCollection {
             return fileCollection.asFileTree.matching { it.include { elem -> isSatisfiedBy(elem.file) } }

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/utils/compatibiltiy.kt

@@ -31,7 +31,7 @@ import org.gradle.util.GradleVersion
 import java.io.File
 import java.io.Serializable
 
-const val minSupportedGradleVersion = "6.7.1"
+const val minSupportedGradleVersion = "6.8.3"
 
 internal fun checkGradleCompatibility(
     withComponent: String = "the Kotlin Gradle plugin",