hotfix: revert shadow plugin upgrade (#3298)

Revert "Update dependency com.gradleup.shadow:shadow-gradle-plugin to v9 (#3281)"

This reverts commit a6da595.

Author: PierreSchwang

buildSrc/build.gradle.kts

@@ -23,7 +23,7 @@ val properties = Properties().also { props ->
 dependencies {
     implementation(gradleApi())
     implementation("org.ajoberstar.grgit:grgit-gradle:5.3.2")
-    implementation("com.gradleup.shadow:shadow-gradle-plugin:9.1.0")
+    implementation("com.gradleup.shadow:shadow-gradle-plugin:8.3.9")
     implementation("io.papermc.paperweight.userdev:io.papermc.paperweight.userdev.gradle.plugin:2.0.0-SNAPSHOT")
     constraints {
         val asmVersion = "[9.7,)"

buildSrc/src/main/kotlin/LibsConfig.kt

@@ -45,7 +45,7 @@ fun Project.applyLibrariesConfiguration() {
     )
 
     tasks.register<ShadowJar>("jar") {
-        configurations.set(listOf(project.configurations["shade"]))
+        configurations = listOf(project.configurations["shade"])
         archiveClassifier.set("")
 
         dependencies {

buildSrc/src/main/kotlin/PlatformConfig.kt

@@ -1,4 +1,3 @@
-import com.github.jengelman.gradle.plugins.shadow.ShadowExtension
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 import org.gradle.api.Project
 import org.gradle.api.component.AdhocComponentWithVariants
@@ -36,10 +35,6 @@ fun Project.applyPlatformAndCoreConfiguration() {
         ext["internalVersion"] = "$version"
     }
 
-    configure<ShadowExtension> {
-        addShadowVariantIntoJavaComponent.set(false)
-    }
-
     configure<JavaPluginExtension> {
         disableAutoTargetJvm()
         withJavadocJar()
@@ -50,6 +45,9 @@ fun Project.applyPlatformAndCoreConfiguration() {
     }
 
     val javaComponent = components["java"] as AdhocComponentWithVariants
+    javaComponent.withVariantsFromConfiguration(configurations["shadowRuntimeElements"]) {
+        skip()
+    }
 
     val publishingExtension = the<PublishingExtension>()