Add an error saying that SKIE 2.1.20 requires Gradle 8.8.

Author: FilipDolnik

SKIE/skie-gradle/plugin-impl/src/main/kotlin/co/touchlab/skie/plugin/SkieGradlePluginApplier.kt

@@ -47,6 +47,8 @@ object SkieGradlePluginApplier {
             return
         }
 
+        checkKGPVersionCompatibility()
+
         kgpShim.initializeShim()
 
         warnOnEmptyFrameworks()
@@ -60,6 +62,24 @@ object SkieGradlePluginApplier {
         }
     }
 
+    // TODO Remove once the issue with Kotlin 2.1.20 is resolved
+    private fun Project.checkKGPVersionCompatibility() {
+        val doesNotWorkWithOlderGradleVersions = project.kgpShim.getKotlinPluginVersion().startsWith("2.1.2")
+
+        if (doesNotWorkWithOlderGradleVersions) {
+            val gradleVersionParts = project.gradle.gradleVersion.split(".").mapNotNull { it.toIntOrNull() }
+
+            val majorVersion = gradleVersionParts.getOrNull(0) ?: 0
+            val minorVersion = gradleVersionParts.getOrNull(1) ?: 0
+
+            val gradleIsNotSupported = (majorVersion < 8) || (majorVersion == 8 && minorVersion < 8)
+
+            if (gradleIsNotSupported) {
+                error("SKIE for Kotlin 2.1.20 and newer does not currently support Gradle versions older than 8.8. Please upgrade your Gradle version to at least 8.8.")
+            }
+        }
+    }
+
     private fun SkieTarget.configureSkie() {
         SkieDirectoriesManager.configureCreateSkieBuildDirectoryTask(this)
 

test-runner/src/test/kotlin/co/touchlab/skie/test/base/BaseGradleTests.kt

@@ -66,7 +66,8 @@ abstract class BaseGradleTests: TestUtilsTrait, GradleBuildFileBuilderTrait {
     }
 
     fun runGradle(
-        gradleVersion: String = "8.4",
+        // TODO Revert back to 8.4 once the issue with Kotlin 2.1.20 is resolved
+        gradleVersion: String = "8.8",
         vararg arguments: String = arrayOf("build"),
         assertResult: ((BuildResult) -> Unit)? = {
             assertEquals(TaskOutcome.SUCCESS, it.task(":build")?.outcome)