[Gradle] Adjust jvm target diagnostic message

Do not mention that this diagnostic level becomes error in Gradle 8.0
if the build is using Gradle 8.+ versions.

Some users or plugin may downgrade diagnostic level back to warning, and
this line is misleading for the users.

^KT-80096 Verification Pending

Author: Tapchicoma

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/diagnostics/KotlinToolingDiagnostics.kt

@@ -807,11 +807,19 @@ internal object KotlinToolingDiagnostics {
             jvmTarget: String,
             severity: ToolingDiagnostic.Severity,
         ) = build(severity = severity) {
+            val gradleErrorMessage = if (severity == WARNING &&
+                GradleVersion.current() < GradleVersion.version("8.0")
+            ) {
+                "This will become an error in Gradle 8.0."
+            } else {
+                ""
+            }
+
             title("Inconsistent JVM Target Compatibility Between Java and Kotlin Tasks")
                 .description {
                     """
                     Inconsistent JVM-target compatibility detected for tasks '$javaTaskName' ($targetCompatibility) and '$kotlinTaskName' ($jvmTarget).
-                    ${if (severity == WARNING) "This will become an error in Gradle 8.0." else ""}
+                    $gradleErrorMessage
                     """.trimIndent()
                 }
                 .solution {

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

@@ -229,7 +229,8 @@ internal abstract class DefaultKotlinJavaToolchain @Inject constructor(
                 else -> javaVersion.toString()
             }
 
-            // Update to the latest JDK LTS once it is released and Kotlin has JVM target with this version
+            // Update to the latest JDK LTS once it is released, and Kotlin has a JVM target with this version,
+            // plus the minimal supported Gradle version itself supports it
             return if (javaVersion > JavaVersion.VERSION_17) {
                 try {
                     JvmTarget.fromTarget(normalizedVersion)